FILE – In this Feb. 5, 2007 file photo, Facebook CEO Mark Zuckerberg smiles in this office in Palo Alto, Calif. Zuckerberg turns 28 on Monday, May 14, 2012. He’s considerably younger than the average FORTUNE 500 CEO, of course. But while some investors worry that Zuckerberg is too young to lead Facebook as a public company, experts point out that Bill Gates, Steve Jobs and Michael Dell were in their 20s when their companies had IPOs. (AP Photo/Paul Sakuma, File)