At 14, David Karp—who would one day found Tumblr—was already obsessed with computers and bored with school. So his mom, a science teacher, suggested he drop out. "It became very clear that David needed the space to live his passion. Which was computers," Barbara Ackerman tells the New York Times. Her son dropped out to be home-schooled, but ultimately he never finished high school. Instead, he started working with TV producer Fred Seibert, learning everything he could about engineering; ultimately, he built a video app for Seibert that was one of the first to be sold on iTunes. From there he moved to other startups before ultimately starting his own company in 2006 and then founding Tumblr.
Now 26, Karp is a Mark Zuckerberg-like, sneakers-and-jeans-wearing entrepreneur (his response to Yahoo's $1.1 billion acquisition of Tumblr this week: "F--- yeah.") who has been a somewhat controversial figure, often blogging about partying and showing up on the gossip pages. He's currently fighting rumors that investors want to replace him as Tumblr's CEO. But there's no arguing with his success; he'll reap an expected $250 million from the Yahoo deal, and he already lives in a $1.6 million Brooklyn loft with his girlfriend of four years. What's next for him? Maybe college—"At least I should be able to afford it," he says—and some sort of philanthropy. (Read more David Karp stories.)