Jon Ronson: When online shaming spirals out of control

Twitter gives a voice to the voiceless, a way to speak up and hit back at perceived injustice. But sometimes, says Jon Ronson, things go too far. In a jaw-dropping story of how one un-funny tweet ruined a woman's life and career, Ronson shows how online commenters can end up behaving like a baying mob -- and says it's time to rethink how we interact online.