Facebook, the world's largest social network

Facebook, the world's largest social network, announced in July 2010 that it had 500 million users around the world. The company has grown at a meteoric pace, doubling in size since 2009 and pushing international competitors aside. Its policies, more than those of any other company, are helping to define standards for privacy in the Internet age.

The company, founded in 2004 by a Harvard sophomore, Mark Zuckerberg, began life catering first to Harvard students and then to all high school and college students. It has since evolved into a broadly popular online destination used by both teenagers and adults of all ages. In country after country, Facebook is cementing itself as the leader and often displacing other social networks, much as it outflanked MySpace in the United States.

But it has also come to be seen as one of the new titans of the Internet, challenging even Google with a vision of a Web tied together through personal relationships and recommendations, rather than by search algorithms. In a major expansion, Facebook has spread itself across other Web sites by offering members the chance to "Like'' something — share it with their network — without leaving the Web page they're on.