When people encounter Craig Newmark they can't believe they're meeting the Craig. It seems that the founder of craigslist.org--the wildly popular Internet site that's becoming the world's bulletin board--has reached the single-name status of Arnold, Cher and Madonna. The fame is surprising to the plump, bald, 52-year-old former computer programmer. "I'm just keeping it very simple," says Newmark.

Simple is almost a religion at craigslist. Begun in 1995 as an e-mailed dispatch of San Francisco job leads and apartment vacancies, the list now covers more than 75 cities, from Anchorage to Zurich. Six million people every month use the free service to search for jobs, junk, tickets, apartments, roommates, mates and temporary intimates--often requested with shocking specificity.

What will undoubtedly prove not simple for Newmark and his CEO Jim Buckmaster, is managing the list's meteoric growth while maintaining what Craig refers to as "nerd values." Essentially, that means being smart and open about making the world a better place. It also seems to encompass an aversion to frills. Headquarters is a battered Victorian house in San Francisco's Sunset district. The craigslist Web site is even less ostentatious: its design is reminiscent of the scrap of paper you use for the office football pool. Nonetheless, the list is a sleeping economic giant that's already dishing nightmares to ticket scalpers, employment brokers and publications that live by classified ads. "Craigslist has had an impact on our revenues--because it's free," says David Schneiderman, CEO of Village Voice Media.

Newmark, who spends the bulk of his time purging spammers and con artists from the list, insists that he won't change course. So far the only concession to mammon is a fee for help-wanted notices in certain cities, reaping almost $10 million a year. Even eBay's purchase of a 25 percent stake in the company (from a minority shareholder) won't change the craigslist culture. And if moralists gripe about the sexual matchmaking, he'll snap right back. "We're talking about values of the highest kind," says Newmark. "Helping out people."