A person poses with a cell phone in front of a computer screen to check Barack Obama's tweet on November 7, 2012 in Paris after his re-election as US president. Barack Obama brought his sophisticated social media campaign to an emotional climax, proclaiming his victory on Twitter and Facebook just as TV networks were breaking the news. The post was his most re-tweeted -- 472,000 shares in three hours -- according to Twitter's politics account @gov. It was also the most popular ever, topping a message from singer Justin Bieber, website BuzzFeed said. AFP PHOTO / LIONEL BONAVENTURE (Photo credit should read LIONEL BONAVENTURE/AFP/Getty Images)
