U.S. President Barack Obama, left, shares a laugh with Mark Zuckerberg, co-founder and chief executive officer of Facebook Inc., during a town hall event at Facebook headquarters in Palo Alto, California, U.S., on Wednesday, April 20, 2011. Obama said members of both political parties in Washington need to work together to start reducing the nation's budget deficit in a « balanced way. » Photographer: David Paul Morris/Bloomberg via Getty Images *** Local Caption *** Barack Obama; Mark Zuckerberg