4. Evan Williams, CEO, Twitter
It's hard to argue about just how rapidly Twitter has changed the social networking landscape. A lot of the credit goes to Twitter's Evan Williams, who grew up on a farm in Clarks, Neb. These days Williams is thinking about how he can harvest revenue from the innovative micro-blogging service. We don't know what exactly Williams' plan is to make money from Twitter. We do know that it would be a mistake to underestimate Twitter's power.