That these works are sometimes fake or misleadingly labeled is no surprise to art experts and to foundations that monitor online art sales. But fraud has saturated certain sectors of the art market, experts say. 

“In every country that I visit, even Abu Dhabi, I’m approached by artists or estates who are desperate about the fake situation,” said Véronique Wiesinger, the director and senior curator of the Alberto and Annette Giacometti Foundation in Paris. “We counted the other day 2,005 fake Giacometti sculptures for sale” on just one Web site, she added. 

Many reputable online sellers, of course, deliver precisely what they advertise. “There is a lot of buying online, and most people are satisfied,” said Alan Bamberger, an art consultant and appraiser. 

Over the last few years the Internet has broadened the art market far beyond the exclusivity and opaque jargon of its moneyed enclaves and has helped turn the slogan “art for everyone” into reality. But it has also become a sort of bazaar, where shoppers of varying sophistication routinely encounter all degrees of flimflammery, from the schemes of experienced grifters to the innocent mistakes of the unwitting and naïve. A recent study by statisticians at George Washington University and the University of California, Irvine, estimated that as many as 91 percent of the drawings and small sculptures sold online through eBay as the work of the artist Henry Moore were fake.