Last summer Wired magazine ran a cover story on Craigslist, the classified-advertising Web site, and its founder, Craig Newmark. Craigslist, the headline read, was a mess. The story said the site was underdeveloped. It refused to monetize itself. Mr. Newmark wouldn't add new features, and his motivations were obscure.

Indeed, so poorly is Craigslist run that it's easily one of the 20 biggest Web sites in the U.S. and, according to Wired, likely topped $100 million in revenue last year. It did this with minimal effort and...