The opening of Art Basel Miami Beach, under way here this week, looked like the start of the most glamorous doorbuster sale in history, with hundreds of V.I.P.'s streaming into the convention center wearing high-end resort casual, ready to rummage through more than 200 of the world's most prestigious galleries.
Among the shoppers were prominent collectors like Peter Brant, the newsprint executive, who strolled with the actor Owen Wilson. At the Gagosian Gallery booth, P. Diddy gave a hug to the casino mogul Steve Wynn beside a $2 million sculpture by Roy Lichtenstein.
But one notable titan of this realm was missing: Steven A. Cohen, the hedge fund billionaire, who in less than six years has acquired one of the market's richest troves, with works by Manet, Monet, Jackson Pollock, Andy Warhol and Damien Hirst, to cite just a few.
In recent weeks, his name has surfaced with the legal troubles of Mathew Martoma, whom federal prosecutors have accused of insider trading while working at Mr. Cohen's firm in Connecticut, SAC Capital Advisors. Mr. Cohen has not been charged with any wrongdoing, but there has been speculation that the government hopes to leverage the case against Mr. Martoma into charges against Mr. Cohen.
Does that possibility worry luminaries in the art world? A quick survey of gallerists, advisers and collectors suggests it depends on whom you ask. Plenty of people doubt that Mr. Cohen will ever be in genuine jeopardy and others think that even if he is, the art market now has so many well-heeled players that the absence of one buyer wouldn't have a notable impact.
Then there were the gallery owners who had sold works to Mr. Cohen. As a general rule, the more business they have conducted with the man, the more worried they are likely to be.
"It's disconcerting," said Timothy Blum, co-owner of Blum & Poe, a gallery in Los Angeles. "We're talking about a lot of liquid," he added, meaning money. "A lot of liquid. I've never calculated it out, but he's responsible for a significant percent of our business."
For Mr. Blum and other elite gallery owners, there is sincere dread at the notion, however remote, that Mr. Cohen may one day be sidelined. Known in the securities world for astounding investment returns and an occasionally volcanic temper, he is described by dealers as the ideal collector — warm, dedicated, eager to take home the best pieces and unafraid to spend what it takes.
"We would absolutely hate to have him not active in the market, I can wholeheartedly say that," said David Zwirner, who owns a gallery that bears his name in the Chelsea section of Manhattan. "This man is a friend of mine. I called him last week — 'How are you? What's going on?' I think the art world is rooting for him. I'm rooting for him. I wish he were here right now."
Two years ago, Mr. Cohen arrived at Mr. Zwirner's booth in the opening minutes of the V.I.P. preview day and dropped $300,000 on a work by Adel Abdessemed, an Algerian-born artist who lives in Paris. Within the hour, Mr. Cohen had reportedly spent an additional $180,000 at Blum & Poe for a work by Tim Hawkinson called "Bike."
The fair didn't officially open until Thursday, but on Wednesday the convention center was already radiating an air of unabashed opulence. Cavernous, and crammed with product, the place is a kind of Costco for the rich, where the prices range from a low of a few thousand dollars to a high of "we don't give out that information." Women pushing carts handed out free flutes of Ruinart Champagne, the official Champagne of Art Basel Miami Beach.
Will Ferrell, the comedian, was one of handful of celebrities in the crowd. Wearing mirrored aviator sunglasses and sporting a green shirt with "Ireland" emblazoned on the back of the neck, he said he already knew what he wanted.
"The sponge cake," he deadpanned, nodding toward a cube of marble covered with frostinglike swirls, a work by the Chinese artist Ai Weiwei. "They don't know it yet," he said, referring to the dealers at Lisson Gallery, where the block sat. "But it's done."
Several people who were asked about Mr. Cohen described prosecutors' apparent pursuit of him as a witch hunt. Eli Broad, a businessman and philanthropist with one of country's most significant art collections, took a quick break from browsing on Wednesday to say that all the talk about Mr. Cohen is "a lot of gossip. And the art world loves to gossip."
This may be true, but many in the art world are also reluctant to forecast what it may mean if Mr. Cohen ends his shopping sprees at fairs or stops waving paddles at the auction houses. (Or, to be more precise, stops hiring a consultant to wave on his behalf.) Those willing to speculate thought it was a bit premature to speculate.
"I don't mean to sound cavalier but there is this sense at this point that this is much ado about nothing," says Todd Levin of the Levin Art Group, an art consulting firm. "If there were actual allegations by the S.E.C. and those turned into actual charges and if it actually went to trial, then we'd have something to talk about. Until then, I don't think anyone is paying attention to this."
That said, if the worst happened to Mr. Cohen and he wound up in prison, "would there be an effect?" asks Mr. Levin. "Sure, but only in the super, super, superhigh end of the modern and contemporary markets. There would still be plenty of people buying in the eight-figure range and plenty buying in the seven-figure range. There are a lot of really wealthy people in the world, in Brazil, England, other parts of Europe, China. If one billionaire stops buying art, it's unfortunate, but the world goes on."
Because Mr. Cohen has so much money, he is unlikely to ever have to sell his collection, experts say. But if he did, he would probably find many willing buyers. History suggests that any tarnish that might attach itself to the reputations of people doesn't touch their art assets. Mr. Cohen's well-regarded eye would probably give his works a greater value.
But those who say they believe the art market would be unfazed by Mr. Cohen's absence are saying something about the market itself, which is now more diverse than ever. "Five or six years ago, all this talk about Steve Cohen might have been quite significant," says Anders Petterson of ArtTactic, an art market research company based in London, "but he's now just one of many big fish in this pond."