Facebook is the world's largest social network, with 750 million users worldwide as of July 2011. More than any other company, it is defining what some see as the "social'' era of the Internet. And its policies, more than any others, seem to be driving the definition of privacy in this new age.

The company, founded in 2004 by a Harvard undergraduate, 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 has cemented itself as the leader and often displacing other social networks. 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.

The company's rise has been marked by strings of controversies. Three other Harvard students maintain that they came up with the original idea and that Mr. Zuckerberg, whom they had hired to write code for the site, stole the idea to create Facebook.

"The Social Network," a movie released in 2010 about Facebook’s tumultuous origins, offered up what A.O. Scott called "a creation story for the digital age and something of a morality tale, one driven by desire, marked by triumph, contaminated by betrayal and inspired by the new gospel: the geek shall inherit the earth."

Mr. Zuckerberg disputed the characterization of him in the film, though in a New Yorker magazine profile, he acknowledged having indulged in a bit of immature arrogance.

_{(Adapted from: http://topics.nytimes.com/top/news/business/companies/facebook_inc/index.html. )}

In July 2011, Facebook