Facebook, of course, got its start in Zuckerberg's messy Harvard dorm room in early 2004. Known as Thefacebook.com in those days, the site was created to help Harvard students — and later other college students — connect with one another online. The scrappy website later grew to include high-schoolers, then anyone else with an Internet connection. Today more than 900 million people log in at least once a month, making Facebook the world's definitive social network.
All along, Zuckerberg has shown a maturity beyond his years. As the site grew rapidly and caught the eye of big media and rival Internet companies, Zuckerberg consistently rebuffed mouth-watering buyout offers, including those from Google Inc. and Yahoo Inc.
"Simply put: we don't build services to make money; we make money to build better services," Zuckerberg wrote in his letter to prospective shareholders. "And we think this is a good way to build something. These days I think more and more people want to use services from companies that believe in something beyond simply maximizing profits."
People who've observed Zuckerberg closely say his age is an asset. His is the generation that grew up with social networking, with computers all around them and the Internet as something that's always existed. Many of his employees are younger than him, as are a lot of the up-and-coming technology entrepreneurs with whom he competes.
"I don't think you could build a company like this if you were an old guy like me," says David Kirkpatrick, a 59-year-old author who chronicled the company's early history in "The Facebook Effect."
Kirkpatrick, who is also founder of Techonomy, a media company that hosts conferences on the relationship between technology and economy and social progress, first met Zuckerberg six years ago. He says he was impressed with his vision, even then.