Facebook is an online social networking service headquartered in Menlo Park, California. Its website was launched on February 4, 2004, by Mark Zuckerberg with his Harvard College roommates and fellow students Eduardo Saverin, Andrew McCollum, Dustin Moskovitz and Chris Hughes. The founders had initially limited the website's membership to Harvard students, but later expanded it to colleges in the Boston area, the Ivy League, and Stanford University. It gradually added support for students at various other universities and later to high-school students. Since 2006, anyone who is at least 13 years old was allowed to become a registered user of the website, though the age requirement may be higher depending on applicable local laws. Its name comes from a colloquialism for the directory given to it by American universities' students.
A big part of Facebook's pitch is that it has so much information about its users that it can more effectively target ads to those who will be responsive to the content. If Facebook can prove that theory to be true, then it may not worry so much about losing its cool cachet.
Entrance to Facebook's previous headquarters in the Stanford Research Park, Palo Alto, California
Entrance to Facebook headquarters complex in Menlo Park, California
Inside the Facebook headquarters in 2014
Facebook popularity. Active users of Facebook increased from just a million in 2004 to over 750 million in 2011.
Population pyramid of Facebook users by age as of January 1, 2010
Kramer et al. (2014) found a 0.07% — that's not 7 percent, that's 1/15th of one percent!! — decrease in negative words in people's status updates when the number of negative posts on their Facebook news feed decreased. Do you know how many words you'd have to read or write before you've written one less negative word due to this effect? Probably thousands.