Entrepreneurs grapple with building or selling

Facebook struck its first major financial partnership last summer with Microsoft, which reportedly guaranteed to deliver about $200 million in ad revenue through 2008. Zuckerberg said the advertising contract with Microsoft recently had been extended through 2011. Terms of the extension haven't been disclosed.

Although he dropped out of Harvard in 2004 to move Facebook to Silicon Valley, Zuckerberg still leads the ascetic lifestyle of a college student even as he runs a business with 200 employees.

Zuckerberg says he keeps little more than a mattress in his apartment, which is located just a few blocks away from Facebook's office. The proximity allows him to walk to work every day, usually wearing Adidas sandals ideally suited for lounging around a campus dorm.

Being comfortable is important to Zuckerberg because, like so many of the Silicon Valley prodigies before him, he tends to spend long hours at the office plotting strategy.

"For now, I just think it's very important to have a good sense of direction about where we are going," he said.