America's Youngest Billionaires

Facebook catapults three 20-somethings onto the list.

The Facebook phenomenon strikes again, this time helping catapult two new 20-somethings into the ranks of America's richest for the first time and bringing down the average age of America's richest to 65.7. Only eight American billionaires are under the age of 40, and three of them co-founded Facebook.

The youngest? The world's youngest billionaire is now 26-year-old Dustin Moskovitz, who is eight days younger than his former Harvard roommate and Facebook co-founder Mark Zuckerberg. The social-networking site's first chief technology officer, Moskovitz left in 2008 and started Asana, a software company that allows individuals and small companies to better collaborate.

The third Facebook co-founder among the ranks is 28-year-old Eduardo Saverin, who once owned a one-third stake in Facebook. When Zuckerberg and Moskovitz quit school to relocate to California, Saverin stayed behind to graduate. 

Technology, and in particular the Internet, has long been the best bet for getting rich at a young age. Bill Gates made his debut on the list in 1986 at age 30 with a net worth of $315 million. Michael Dell debuted at age 26; 19 years later, he is still among the list's 20 youngest. Indeed half of the 20 youngest America billionaires have made their fortunes in the tech industry, most via the Internet.

Outside the world of the Internet, young rich-list members have been able to cash in from a few other industries such as finance and sports.

Worth noting about this bunch is not simply how quickly they've made their money, but how they are choosing to spend it, not so much on luxury homes or expensive toys but on causes about which they are passionate. Google's Larry Page is buying up chunks of residential Palo Alto for a network of houses that use new types of fuel cells, geothermal energy and rainwater capture. EBay's Pierre Omidyar has donated to everything from a company that designs solar powered lanters to a political satire show in Kenya. Moskovitz gave $70,000 in support of Proposition 19, which is seeking to legalize marijuana in California in November. John Arnold has agreed to take the Giving Pledge, making the commitment to give the majority of his wealth to charity.

As for Zuckerberg, he still lives in a relatively modest rental home in Palo Alto, Calif. So what's he doing with his wealth? Not much so far, given that most of it is tied up in non-public shares of Facebook. Still, the 26-year-old announced on "The Oprah Winfrey Show" in September that he is giving away $100 million to Newark's schools. The gift is the largest philanthropic act by a person his age in American history.