Facebook Founder

Mark Zuckerberg, U.S.
Age 23

$1.5 billion, self-made Tech's newest golden boy founded addictive social-networking site Facebook in February 2004 from his Harvard dorm room. He left school for Silicon Valley that year. Microsoft paid $240 million last October for a 1.6% stake, giving the company an implied valuation of $15 billion. Some analysts and a few Facebook investors think that's high. We think Zuckerberg's stake is worth $1.5 billion. Regardless, Zuckerberg is the youngest billionaire on earth and possibly the youngest self-made billionaire ever.