Mark Zuckerberg, 23, founded Facebook while studying psychology at Harvard University. A keen computer programmer, Mr Zuckerberg had already developed a number of social-networking websites for fellow students, including Coursematch, which allowed users to view people taking their degree, and Facemash, where you could rate people’s attractiveness. In February 2004, Zuckerberg launched “The facebook”, as it was originally known; the name taken from the sheets of paper distributed to freshmen, profiling students and staff. Within 24 hours, 1,200 Harvard students had signed up, and after one month, over half of the undergraduate population had a profile.

The network was promptly extended to other Boston universities, the Ivy League and eventually all US universities. It became Facebook.com in August 2005 after the address was purchased for $200,000. Just a week later after Zuckerberg launched his website he was accused of hacking the idea from three Harvard seniors and that soon escalated to a lawsuit. Later in February 2008 the lawsuit was settled with $65 million. US high schools could sign up from September 2005, then it began to spread worldwide, reaching UK universities the following month. As of September 2006, the network was extended beyond educational institutions to anyone with a registered email address. Yahoo and Google are among companies which had expressed interest then in a buy-out, with rumoured figures of around $2bn being discussed.

2009 onwards, Facebook acquired other social media products like real-time news aggregator FriendFeed,  Malaysian contact-importing startup Octazen Solutions, photo-sharing service called Divvyshot, photo sharing service Instagram, and the famous WhatsApp Inc., a smartphone instant messaging application for $19 billion  in a mix of stock and cash, the most ever paid for a venture-capital backed startup.

In September 2014, Facebook valuation crossed $200 billion, making it largest social media company. At the end of 2014, active users on facebook were 1.4 billion. Facebook warehouse stores upwards of 300 PB of data, with an incoming daily rate of about 600 TB.

Reference:

http://en.wikipedia.org/wiki/Facebook

http://www.theguardian.com/technology/2007/jul/25/media.newmedia

http://www.bloomberg.com/infographics/2014-09-08/facebook-valuation-tops-200-billion.html

http://www.statista.com/statistics/264810/number-of-monthly-active-facebook-users-worldwide/

https://code.facebook.com/posts/229861827208629/scaling-the-facebook-data-warehouse-to-300-pb/

http://en.wikipedia.org/wiki/History_of_Facebook