Now, eBay bills itself as “The World's Online Marketplace,” and no competitor is positioned to dispute that claim. More than 724,000 Americans are professional eBay sellers, earning all or most of their annual income from auction sales, Web stores, and other activities on eBay. Another 1.5 million people are supplementing their income by selling on eBay. These figures were reported in a 2005 survey conducted for eBay by ACNielsen International Research. According to an eBay news release, “The number of eBay entrepreneurs in the U.S. has increased 68 percent since the last time a comparable study was conducted in 2003. That study indicated that 430,000 Americans at the time were making some or all of their income selling on eBay.”

In estimates from other sources, eBay now controls 80 to 85 percent of the online auction market, with Yahoo! and Amazon running distant second and third. In the first six months of 2005, eBay's members sold merchandise worth nearly $11 billion dollars, ranking the Web site ahead of some countries in economic output.

What types of items are the best sellers on eBay? Some observers say computer equipment, networking devices, and consumer electronics are tops, followed by videos and DVDs, video games, and house and garden items. But the fact remains, with tens of millions of active buyers and sellers online at one time, virtually anything can be bought or sold at an online auction.