Last week, London hosted three major art fairs and several smaller and younger ones, enough to make any sane person wonder: have we reached the point of art fair overkill? I’ve often thought—and written—that the art fair scene has gone overboard, and now I’m not alone. On his Facebook page New York magazine’s art critic Jerry Saltz recently lamented the explosion of art fairs and the new custom among hungry galleries to send out email blasts from them announcing how many works they’ve sold. “We’ve built a worm into the system,” Mr. Saltz wrote. “The system is self-supporting and draws its power from everyone.” The point is timely, because London’s annual Frieze art fair—the highlight of a week of art parties and hobnobbing in British style—has sprouted a second fair, Frieze Masters, for more “historical” artworks. I was there for the opening of Masters, and it forced me to change my tune. And so, in the words of the great Marcel Duchamp, I will now “force myself to contradict myself in order to avoid conforming to my own taste.”

Since 2003, Frieze has brought dozens of galleries from all over the world to London every October, and showcased some of the best and worst in cutting-edge contemporary art. The show happens under an architect-designed big top in Regent’s Park, and it has been a smashing success since its inception, drawing thousands of buyers and gawkers who feast their eyes and empty their wallets on fresh pieces of art. By riding the Saatchi wave of hipness and hotness in British art, Frieze founders Amanda Sharp and Matthew Slotover succeeded in crowning London as the world’s second great capital of contemporary art. For one crazed week every year, London’s parties and gallery openings rival anything New York can offer.

So, in 2012, has the sinking world economy affected London’s weeklong art bonanza? Apparently not, since several New York galleries continue to open across the pond in a big way. There was plenty of “friezing” at the opening of Pace’s brand-spanking-new space in the Royal Academy building, which featured the unlikely pairing of painter god Mark Rothko with Japanese photographer Hiroshi Sugimoto. Then there was the opening of a swanky new townhouse outpost for David Zwirner, who presented a large Luc Tuymans show well-tailored to European taste. There was even an all-new gallery for Milan’s ever-popular Massimo De Carlo featuring new work by Piotr Uklanski, as well as sundry other extensions, expansions and pop-up shops.

With so much going on, it seems that now almost everyone is saying that art fairs are “out of control.” I’ve thought so for quite a while, yet when I satirized Art Basel Miami Beach less than a year ago, some readers were confused, while others, like Mr. Saltz, attacked me as if I had committed heresy against their church. Funny how quickly the tide turns in art’s little pond. In his Facebook post last Friday, Mr. Saltz proved he’s a switch hitter, rightly pointing out that we have “a hundred art fairs and international biennials … skyrocketing prices during a worldwide economic contraction. The art world’s reflexes are shot; its systems so predetermined that they’re driving us; we’re no longer driving them.”

This may be true, but the dynamic has changed for good and there’s no turning back. I can no longer think of the art fair phenomenon as “out of control,” because the fairs are the ones firmly in control. They control a large percentage of gallery sales, and therefore exert a big influence on the size and shape of art; they are a huge force behind art-buying habits and tastes. Fairs are no longer a good or bad thing, they are the thing, the new reality. Fewer and fewer people go to gallery shows, because sadly, people just don’t have the time or the interest. Or perhaps it’s just easier and more fun to show up in London, Miami, Rio or Dubai to see your friends and party like a rock star, while picking up a painting by a hot artist. These days, art fairs are the only weapons smaller galleries can wield against the large and ever-more-powerful auction houses, which continue their incursion even outside the sales rooms, with the expansion of their own privately brokered art sales. Fairs give the art-buying experience an auction-house sense of urgency, and those impulse sales keep many smaller galleries afloat.

Understanding the delicate balance between art and the art market is where the founders of Frieze have proven their mettle. Remember last May when they launched Frieze New York on Randall’s Island and drew dozens of galleries from around the world? Back then, I thought New York needed another art fair like I needed a root canal, but I was wrong. It was a big success—the place rocked, and it was packed. I was at first skeptical about the new London fair, Masters, which ran simultaneously with Frieze in another tent, across Regent’s Park: why would a company cannibalize its own business by running two fairs in the same town at the same time? The stated charter included only a subtle difference between the venues: “old” Frieze (now called Frieze London) shows only newish work, whereas new Frieze (Frieze Masters) is limited to “oldish” art. The criterion for “old” seemed pretty random: the work merely had to predate the year 2000, meaning in order to qualify for inclusion, it only had to be 12 years “old”!

AFTER thieves broke into the Kunsthal Museum in Rotterdam, the Netherlands, on Monday night and stole a king’s ransom’s worth of paintings by the likes of Picasso, Monet, Matisse and Gauguin, the public and the press were shocked. As usual, a combination of master art thieves and faulty security was blamed. But this seductive scenario is often, in fact, far from the truth.

Most of us envision balaclava-clad cat burglars rappelling through skylights into museums and, like Hollywood characters, contorting their bodies around motion-detecting laser beams. Of course, few of us have valuable paintings on our walls, and even fewer have suffered the loss of a masterpiece. But in the real world, thieves who steal art are not debonair “Thomas Crown Affair” types. Instead, they are the same crooks who rob armored cars for cash, pharmacies for drugs and homes for jewelry. They are often opportunistic and almost always shortsighted.

Take the 1961 theft of Goya’s “Duke of Wellington” from the National Gallery in London. While all of Britain believed that the Goya was taken by cunning art thieves, it was actually taken by a retired man, Kempton Bunton, protesting BBC licensing costs. (He apparently stole the painting by entering the museum through a bathroom window.) In 1973, Carl Horsley was arrested for the theft of two Rembrandts from the Taft Museum in Cincinnati. Later, after serving a prison term, he was arrested for shoplifting a tube of toothpaste and some candy bars.

The illicit trade of stolen art and antiquities is serious, with losses as high as $6 billion a year, according to the F.B.I. There have been teams of thieves who have included art among their targets, like the ones who stole a Rembrandt self-portrait from the National Museum in Stockholm in 2000. (The only buyer they found was an undercover F.B.I. agent.) But in general, it is incredibly rare for a museum to fall victim to a “professional” art thief. The reason is simple: the vast majority of people who steal art do it once, because it is incredibly difficult and because it is nearly impossible to fence a stolen masterpiece.

The wide attention that a high-value art heist garners makes the stolen objects too recognizable to shop around. And there are very few people with enough cash to purchase a masterpiece — even for pennies on the dollar — that they can never show anyone. Once an art thief realizes this, he turns to other endeavors. Meanwhile, the stolen treasures lie dormant in a garage or crawl space until he figures out what to do with them.

It’s easy — and sometimes justified — to criticize security systems as flawed or inadequate, but securing a museum is uniquely challenging. Consider this: The goal of an art museum is to make priceless and rare art and antiquities accessible to the public. They are among society’s most egalitarian institutions. Contrast that with a jewelry store or a bank, where armed guards and imposing vaults are the norm. No one expects to be able to be alone with diamonds worth thousands, but museumgoers do expect an intimate experience with masterworks worth millions. Clearly, it is a daunting task to provide robust security without disturbing the aesthetics of the artwork and its environment.

So what is the remedy for the all-too-frequent scourge of art theft? Museums must build systems that cannot be compromised by a single error or failure. Thieves should have to overcome several layers of security before they can reach their target and several more on the way out. At the Isabella Stewart Gardner Museum, we took such an approach after the 1990 theft of several masterpieces — a crime that hasn’t been solved. This not only makes it more difficult to steal and get away with stolen art, but it gives the police precious extra minutes to respond to alarms, especially if, as in Rotterdam, they sound at night.

When art is stolen, local law enforcement should focus on the right sort of criminals rather than conjecture about multinational art theft rings. The key to finding these missing needles in the haystack is to make the haystack smaller; homing in on the most likely suspects quickly is essential to recovering the stolen item. The F.B.I.’ s Art Crime Team has gathered impressive intelligence on who steals art and what becomes of it. For instance, they’ve learned that upward of 90 percent of all museum thefts involve some form of inside information. So often the best approach is to look at active local robbery gangs, and to investigate connections between past and present employees and known criminals. Enhanced employee background checks and discreet observation of visitor behavior also help to deter thefts.

Confronting these realities is essential to preventing more pieces of our cultural heritage from being lost.

PARIS — With impeccable timing and taste, thieves in the wee hours of Tuesday morning plundered an art museum in the Netherlands that was celebrating its 20th birthday and made away with seven borrowed paintings, including valuable works by Picasso, Monet, Gauguin, Matisse and Lucian Freud.

The Kunsthal museum in Rotterdam — which was exhibiting a private collection owned by the Triton Foundation — was closed to the public after the theft, but the bare spaces on its walls were visible to photographers through windows in its modern building by Rotterdam’s museum park and busy Maasboulevard.

The theft was the latest alarm about museum security in Europe, now a prime hunting ground for art thieves. In 2010 five paintings, including a Picasso and a Matisse, together valued at about 100 million euros, or about $130 million, were stolen from the Musée d’Art Moderne in Paris; they are still missing.

Police investigators combed the grounds of the museum and studied surveillance video for clues to the burglary, which they said happened about 3 a.m. and set off an alarm linked to a security agency. But by the time police arrived soon after, the works had vanished.

The art, part of a collection amassed by a Dutch investor, Willem Cordia, who died in 2011, was exhibited in public for the first time last week at the Kunsthal, which does not have a collection of its own. The stolen paintings span parts of three centuries: Meyer de Haan’s “Self-Portrait” of 1890 and Gauguin’s 1898 “Girl in Front of Open Window”; Monet’s “Waterloo Bridge, London” and “Charing Cross Bridge, London,” both from 1901; Matisse’s 1919 “Reading Girl in White and Yellow” and Picasso’s 1971 “Harlequin Head”; and Freud’s haunting 2002 portrait “Woman With Eyes Closed.”

The theft “was carefully thought out, cleverly conceived and it was quickly executed, so that suggests professionals,” said Charles Hill, a retired Scotland Yard art detective turned private investigator who went undercover to retrieve a version of “The Scream,” by Edvard Munch, after it was stolen in 1994 in Oslo.

“The volume,” he added, “suggests that whoever stole it owes somebody a lot of money, and it’s got to be a major-league villain.”

“My best guess is that someone doesn’t have the cash to repay a loan,” he said.

Marc Masurovsky, a historian and an expert on plundered art in Washington, noted the possibility that the theft was “a contract job,” adding: “These works were picked out. Could it be they had been targeted well before the theft, and the exhibit was the opportunity to strike?”

Willem van Hassel, the chairman of the Kunsthal’s board, announced the closing of the museum on Tuesday and later held a news conference to declare that adequate security measures had been taken.

At the same conference, the museum’s director, Emily Ansenk, said that night measures involved “technical security,” with no guards but camera surveillance and alarms. Museum officials said that the police had arrived on the museum grounds within five minutes of the alarm.

Ms. Ansenk told reporters that the burglary “has hit the art world like a bomb” and described it “as a nightmare for any museum director.” Kunsthal officials declined to estimate the value of the stolen works, though experts say they are collectively worth many millions of dollars, possibly hundreds of millions. Still, it would be difficult for thieves to sell such easily identifiable artworks, contributing to suspicions about underworld finances.

“I think it’s a form of repayment in kind, a barter — 'I don’t have cash, but I have these paintings,’ ” said Mr. Hill, the art investigator.

Kunsthal officials vowed that the museum would reopen on Wednesday.

-By DOREEN CARVAJAL

Hirshhorn Museum and Sculpture Garden

Ai Weiwei will probably be regarded as the most important artist of the past decade. He is certainly its most newsworthy and arguably its most inspiring. Over the repressions of Chinese authorities, he has used a wide range of resources to broadcast a message of freedom.

Through his art, he has spoken with a voice that also includes those who have been silenced. A dissident under a capricious regime, he has endured trials that have captivated world attention while galvanizing an underground culture at home.

The arrival this week of Mr. Ai's first North American retrospective, "Ai Weiwei: According to What?"—which begins at the Hirshhorn Museum in Washington and travels to three other cities, concluding at the Brooklyn Museum in 2014—is itself newsworthy. That this exhibition largely fails to inspire not only speaks to Mr. Ai's own limitations but also to the challenges and missteps in exhibiting this increasingly multifaceted artist.

It bears remembering that following his youth in a Chinese labor camp and his punk bohemian immersion in 1980s New York, for several years Mr. Ai, now 55, was a member of Beijing's cultural elite. A sly thinker and adept designer, he emerged in the late 1990s along with the booming market for contemporary Chinese art to become a sanctioned and profitable ambassador of the modernized socialist state. In 2008, he even served as the artistic consultant on National Stadium, the "Bird's Nest" centerpiece of the Beijing summer Olympics.

It was the Sichuan earthquake in May of that year that turned Mr. Ai from cultural purveyor to iconoclast. He rightly believed that the tragedy of this event, a thousand miles from Beijing in the heart of rural China, was magnified by the state's refusal to investigate its particularly tragic circumstances: the death of more than 5,000 children due to shoddy school construction.

In the years that followed, Mr. Ai put this belief into action. He visited the devastation, documenting the sites in photos and videos, and organized what he called a "citizens' investigation" to identify and memorialize each child killed in this disaster.

As he pursued this project, Mr. Ai increasingly faced off with the Communist state. He came under surveillance and sustained a beating at the hands of local police, a life-threatening brain injury, the destruction of his studio in Shanghai, 81 days of imprisonment and psychological torture, a state-driven campaign of intimidation, multimillion-dollar charges and fines, and the stripping of his freedom to leave the country—including his plans to attend this North American retrospective.

The Hirshhorn show is an update of the one at Tokyo's Mori Art Museum in 2009, which was organized largely before Mr. Ai's dissident chapter. While the current exhibition brings in some important new pieces, it still feels weighted toward the state-sanctioned years. Even the recent selection largely follows the earlier formula.

Much of this work falls under what I call the Salon style of contemporary Chinese art: Oriental idioms, passed through Pop-art sensibilities, processed into large works with a factorylike finish. Mr. Ai can be particularly taken with Western art's historical references. Several examples here are minimalist-inspired sculptures with flourishes of Chinoiserie. "Cube in Ebony" (2009), carved with a traditional rusticated surface, recalls Tony Smith's "Die." "Moon Chest" (2008), created through traditional cabinet-making techniques, riffs off Donald Judd's "specific objects." "Cube Light" (2008), which is a recent acquisition by the Hirshhorn and also the most oversized, underwhelming piece in the show, is minimalism transformed into a kitschy chandelier.

Too much real estate gets taken up by these large works. The Mori's Mami Kataoka, who also curated this show, calls the art a "warm" minimalism for existing "between formalist and contextual methodologies"—in other words, Western work with an Eastern twist.

It is true that Mr. Ai includes personal, social and political references in his sculptures. At times they can seem like the coded messages of a prisoner tapping on his cell wall. "Surveillance Camera" (2010), a marble sculpture that turns an object of oppression into a work of art, is ominous and poignant. But often the sculpture, outsourced to inexpensive Chinese artisans, is a lot of effort for not much return. Sculptures that require lengthy explanations—that one was inspired by a small wooden box left by the artist's dissident poet father, Ai Qing, or that one was inspired by the shaking of the chandelier in Sergei Eisenstein's 1928 film "October"—are not so much "warm" as warmed over. One exception is "Straight" (2008-2012), a new floor installation made up of 38 tons of rebar recovered from Sichuan after the earthquake that is a rough and powerful work regardless of what else we know about it.

Mr. Ai has always been a conceptual artist. The challenge of a conventional museum exhibition is that his output has become more and more immaterial. It could be that Mr. Ai is now best reflected in other ways—for example in Alison Klayman's inspiring documentary "Ai Weiwei: Never Sorry." Blogging, Twitter and the Internet itself, to which Mr. Ai devotes eight hours a day, have become his genuine new media and his most consequential work. Unfortunately, this traditionally mounted show tells us little about that. Walls of photographs—with both wonderful snapshots from his New York years and thousands of digital images from his Internet feed—could offer extra context, but they are so poorly labeled and hung so high that they serve as little more than decoration.

For a retrospective, there is also regrettably little about his involvement in the Beijing avant-garde of the late 1970s—he was part of the "Stars" group during a brief thaw known as the "Beijing Spring." Nor are there examples of his underground books published in the mid-1990s.

A deep humanity runs through Mr. Ai's best work. "I've experienced dramatic changes in my living and working conditions over the past few years," he says in an interview with Hirshhorn curator Kerry Brougher reproduced in the exhibition catalog. But he resists being taken in by his own politics. "Maybe I'm just an undercover artist in the disguise of a dissident," he says. Believing in "freedom of speech, free expression, the value of life, and individual rights," he tempers his politics with empathy.

That's why his work on the "citizens' investigation" is so affecting and stands apart from the more ornamental aspects of this show. Alongside a wall-size spreadsheet listing all the child victims of the Sichuan quake, including their birthdays and schools, he presents a recording that reads off their names. In this stripped-down piece, we sense the full extent of the loss, a tragedy that is magnified for the victims' parents by China's one-child policy: "These people have cried a lifetime's worth of tears," says Mr. Ai. "In their hearts, they know that the precious lives they gave everything to protect are no longer." Beyond politics, the work strikes at the heart of death and remembrance. It also shows us how present this artist can be even in his absence—and just what is missing in so much else of this exhibition.

-By James Panero