Mark Zuckerberg (2nd ed.)

In February of 2004, 19-year-old Mark Zuckerberg launched a new website from his Harvard University dorm room, one inspired by "face books," or college student directories with photos and information about the students. Taking a cue from Bill Gates, Zuckerberg dropped out of Harvard to devote his full time to his new social networking site. That site, now known as Facebook, would expand to the world, with one billion users by 2012. Read about the rise of the young entrepreneur and billionaire wh