Alexis Ohanian, Reddit

Alexis Ohanian co-founded Reddit together with friend Steve Huffman. Reddit has become one of the World Wide Web's most striking examples of democracy in action. Founded in 2005, it grew a user base of tens of thousands and quickly attracted the attention of publisher Condé Nast, which acquired it in 2006. Unlike "social bookmarking" sites, Reddit fashions itself a platform for "social news," where the readers themselves control the front page by voting stories up above and down below the fold.

Ohanian left Reddit in his official capacity in 2009, but continues to be involved with the site's direction as a sort of godfather, dispensing friendly wisdom from his user account, kn0thing. Of late, he's focusing on Breadpig, a hub for geeky books and merchandise. In early 2010, he'll spend three months in Armenia as a Kiva Fellow.