Age: 27
Occupation: Co-founder, chairman and CEO of Facebook
Ever since launching his revolutionary social network in 2004, Zuckerberg has been one of the most influential business leaders in the world. And 2012 will be a banner year for Facebook as it plans an initial public offering that could value the firm at as much as $100 billion — a deal that will make majority owner Zuckerberg a very wealthy man indeed but bring with it a whole new series of pressures and expectations.