Facebook is a social networking service launched in February 2004, owned and operated by Facebook, Inc. As of September 2012, Facebook has over one billion active users, more than half of them using Facebook on a mobile device. Users must register before using the site, after which they 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, and categorize their friends into lists such as "People From Work" or "Close Friends". Users can create profiles with photos, lists of personal interests, contact information, and other personal information. Users can communicate with friends and other users through private or public messages and a chat feature. They can also create and join interest groups and "like pages" (called "fan pages" until April 19, 2010), some of which are maintained by organizations as a means of advertising. Facebook has been prompted to add a "third gender", "other", or "intersex" tab in the gender option which contains only male and female. Facebook refused and said that individuals can "opt out of showing their sex on their profile". A 2012 Pew Internet and American Life study identified that between 20–30% of Facebook users are "power users" who frequently link, poke, post and tag themselves and others.
Miłosz Szarek @ Facebook