Investigative series looks at Facebook and politics

Politics and social media go hand-in-hand, sometimes for good and sometimes not. Pulitzer Prize-winning reporter Dana Priest investigated how Facebook went from idealistic to something else. In the early days, a gangly, t-shirt-wearing kid named Mark Zuckerberg said the mission of the social network was to unite the world. So when did it change? And can Facebook really affect the outcome of the elections?