In the hipster enclave of Williamsburg, Brooklyn, Tumblr founder and CEO David Karp is “quite possibly the richest person in the neighborhood,” said Jeff Bercovici in Forbes. The 26-year-old’s social networking site, where users can post photos, texts, songs, and other expressions of individual quirkiness, edged out Microsoft’s Bing in November to become one of the top 10 online destinations. Karp’s 25 percent share in Tumblr was valued at $200 million in 2011, and its traffic has doubled since then. “The growth we’ve seen in the last year just totally overshadows everything that came before it,” says Karp. But now he’s under rising pressure to prove that he is the man who can lead Tumblr to “actually make money.” 

Karp’s youth doesn’t mean he’s callow, said Cadie Thompson in He has been in business since age 11, when he started designing websites for clients, enlisting his father to make any necessary phone calls so they wouldn’t know he was just a kid. He dropped out of high school, then “skipped college altogether” so he could build his business. And he has no intention of letting Tumblr slip from his control now. “I want this to be a company I can work for in 30 years,” he says.