Facebook and similar sites to Facebook

Facebook is a social networking website. On the site, users can define their profile- add pictures, notes, and much more, add friends and make new ones. Facebook is now the biggest social networking site, and it has over 250 million (!) users around the globe.
About the features, Wikipedia writes:
“Facebook has a number of features with which users may interact. They include the wall a space on every user’s profile page that allows friends to post messages for the user to see, pokes, which allows users to send a virtual “poke” to each other (a notification that tells a user that they have been poked), photos, where users can upload albums and photos, and status, which allows users to inform their friends of their whereabouts and actions. A user’s Wall is visible to anyone who is able to see that user’s profile, depending on privacy settings. In July 2007, Facebook began allowing users to post attachments to the Wall, whereas the Wall was previously limited to textual content only.”
From Wikipedia: http://en.wikipedia.org/wiki/Facebook#Features
On the web, there are many competitors to Facebook. The list can be found at:
Similar sites to Facebook
One of the common sites is the website MySpace.com, which became the most popular social networking site in the United States on 2006.
However, Facebook is now the biggest social networking site and the most profitable one.