Facebook

Only 400 words but got cba, promise to bamf these up soon,  just waiting for effort to return 

Facebook is an online social networking site that was launched in February 2004. Today it has more than 500 millionactive users as of July 2010.

Users can create “profiles” and attach photos, personal information like birthdays, parties etc. and upload a “status”. All of these can be commented on or “liked”. Chat can be done publically in the comment sections, privately in an incorporated IM feature. Likewise, users can leave public messages on their wall or privately through an internal e-mail system. Users can also create and join interest groups and "like pages" which range from jokes, ideas or forms of media/art like films or TV. Some of these are maintained by organizations as a means of advertising or are simply fan run.
In addition the site runs a variety of flash based games such as MafiaWars and Farmville, which have grown to be incredibly successful, becoming a business venture of their own and incorporating real life money.
The site is free to join and revenue is made by advertising banners dotted around the page. Users are able to manage their own security stating who and under what conditions people can view their profiles. It is requirement that users use their real name instead of a username and features no customizability unlike competitor MySpace.
Facebook also allows users to upload an unlimited amount of photos, putting it ahead of other dedicated sites like Photobucket or Flickr.
The site itself is very minimalist, utilising a simple white and blue colour scheme for all it's pages. The interface can be split into two parts, profile pages and the wall. Everything from apps to games to users has an individual profile page with links to associated images abd information. On the other hand a user has a dedicated wall built for them, a collage of status updates and recent activity that is tailored to show the user what they want to see based on number of interactions with that user and individual selections to hide unwanted content.
Much of Facebooks success can be attributed to it's universal adoption by so many people, regardless of the quality of the site the shear amount of users would encourage people to follow the trend and sign up. The vast amount of services rolled into one account and the slick minimalist presentation only add to the perfect storm of social networking.