Facebook (stylized facebook) is a social networking service and website launched in February 2004, operated and privately owned by Facebook, Inc. As of January 2011, Facebook has more than 600 million active users. Users may create a personal profile, add other users as friends, and exchange messages, including automatic notifications when they update their profile. Additionally, users may join common interest user groups, organized by workplace, school or college, or other characteristics. The name of the service stems from the colloquial name for the book given to students at the start of the academic year by university administrations in the United States to help students get to know each other better. Facebook allows anyone who declares themselves to be at least 13 years old to become a registered user of the website. (Excerpt from <a href="http://en.wikipedia.org/wiki/Facebook">Wikipedia article: Facebook</a>)Percentage of Ariadne articles tagged with this term: [term_node_prcnt_1]%.