Facebook is a social networking service and website started in February 2004. It is owned by Facebook, Inc.[6]As of September 2012, Facebook has over one billion active users.[7] Users may make a personal profile, add other users as friends, and send messages. Facebook users must register before using the site. Users may join user groups. These groups can be for a workplace, school or college, or other interest. The name of the service comes from the name for the book given to students at the start of the school year by some universities in the United States. These books help students get to know each other better. Facebook allows any users who say they are at least 13 years old to become users of the website.

Facebook was started by Mark Zuckerberg with his college roommates and fellow computer science students Eduardo SaverinDustin Moskovitz and Chris Hughes.[8]The websites membership was only for Harvard students at first. Later it included other colleges in the Boston area, the Ivy League, and Stanford University. It eventually opened for students at other universities. After that, it opened to high school students, and, finally, to anyone aged 13 and over. Based on ConsumersReports.org in May 2011, there are 7.5 million children under 13 with accounts. This breaks the websites rules.[9]

A January 2009 Compete.com study ranked Facebook as the most used social networking service by worldwide monthly active users.[10] Entertainment Weekly put the site on its end-of-the-decade "best-of" list. It said, "How on earth did we stalk our exes, remember our co-workers birthdays, bug our friends, and play a rousing game ofScrabulous before Facebook?"[11] Quantcast estimates Facebook had 138.9 million monthly different U.S. visitors in May 2011.[12] According to Social Media Today, in April 2010 about 41.6% of the U.S. population had a Facebook account.[13] Facebooks growth started to slow down in some areas. The site lost 7 million active users in the United States and Canada in May 2011 relative to previous statistics.[14]