"In 2002, John Wieber started worrying about his business, which sold refurbished computers through Internet auctioneer eBay Inc. Although he was earning $1 million a year in revenue, profits had started to slip as competitors flocked to the site. EBay also raised its fees, further cutting margins, and fraud was becoming a problem.

So Mr. Wieber revamped his Web site and began selling through other online companies, such as Amazon.com Inc. and Yahoo Inc. Last year, his sales neared $5 million, but his eBay revenue grew at a much slower pace, making up only a quarter of the total. It will likely fall still lower. Of the auction site, where he got his start, Mr. Wieber says: 'Too many sellers, not enough buyers.'"