Reid Hoffman, Greylock Partners

Reid Hoffman
LinkedIn, which Hoffman founded, went public in May, and, poof, his 21.7 percent stake was suddenly worth more than $1.6 billion. The stock has slid since then, but Hoffman--already wealthy from eBay's purchase of PayPal, where he was an executive vice president--is doing just fine.

Hoffman, one of the most plugged-in people in Silicon Valley, is currently on the board of freshly public Zynga. He's been a partner with Greylock Partners since 2009, and his portfolio includes such eye candy as Groupon, Airbnb, and Gowalla, which was just bought by Facebook. Somehow it feels as though Hoffman, who's 44, is just getting started.