7. Craig Newmark, Founder, Craigslist
His site has no ads, charges absurdly low fees to a small fraction of its visitors, has a ".org" domain, and employs 23 people. Yet Craigslist has become an addiction for millions, who impulsively refresh the listings of free stuff, "rants & raves," and personal ads while shirking their day jobs. Most importantly, it has almost singlehandedly demolished the offline classified advertising business.