Facebook is a privately-held social networking website which was launched on February 4, 2004.
In the beginning, the membership was restricted to students of Harvard University. It was subsequently expanded to other Boston area schools (Boston College, Boston University, MIT), Stanford, and all Ivy League schools within two months. Many individual universities were added in rapid succession over the next year. Eventually most US college and many Canadian university students with a university (.edu) email address were eligible to join. There was a separate network initiated for US high schools. Since September 2006, it has been made available to any email address user who inputs a certain age range. Users can select to join one or more participating networks, such as a high school, place of employment, or geographic region.
As of July 2007, the website had the largest number of registered users among college-focused sites with over 34 million active members worldwide (also from non-collegiate networks). In July 2007 it was ranked between top 10–13 web sites, and was the number one site for photos in the United States, ahead of public sites such as Flickr, with over 8.5 million photos uploaded daily. It is also the seventh most visited site in the United States.
In a move possibly to rival Google's purchasing of YouTube and keep up with the latest in advertising fashion, Microsoft has purchased a 1.6% stake in Facebook for $240 million. This estimates Facebook's value at $15 billion, priced at over 100 times earnings.
Facebook is also planning to launch SocialAds, its own social ad-network taking Google's Ad-Sense head on.
