In this Nov. 15, 2010 file photo shows Facebook CEO Mark Zuckerberg smiling at an announcement in San Francisco. Another 17 of America's richest people, including Zuckerberg, junk bond pioneer Michael Milken and AOL co-founder Steve Case, have pledged to give away most of their wealth. They are the latest to join the Giving Pledge, an effort led by Microsoft founder Bill Gates and investor Warren Buffett to commit the country's wealthiest people to step up their charitable donations. (AP Photo/Paul Sakuma, file)