Timeline: The Most Important Social-Media Events in History
The first e-mail was sent just over 40 years ago; we've come a long way, baby. But along with the highs (Twitter-enabled revolutions, Chatroulette), there have been a lot of lows (Kim Kardashian's tweets, Chatroulette). These are the moments that are worth remembering and, in some cases, cringing about. Plus: See our complete coverage of social media mavericks.