40 under 40

2. Mark Zuckerberg

Even as Aaron Sorkin's film, The Social Network, portrays a certain fictional Harvard dropout with a mean streak, the real Mark Zuckerberg has made good on his goals this year: Facebook will pull in more than $1 billion in revenue; he unveiled a suite of new social tools; and despite a privacy backlash, the number of active users has jumped to an almost unfathomable 500 million; Facebook has surpassed Google to become the most trafficked site on the web.

New friend: Last month he made a surprise $100 million donation to help Newark's schools.

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Last updated October 14 2010: 1:25 PM ET