A study investigating the phenomenon identified privacy as the biggest reason why people were turning against the social network.
General dissatisfaction with Facebook, fears of internet addiction, and the shallow nature of online friendships also played a part, it said.
With more than 950 million active users, Facebook is far and away the most popular social networking site, followed by Twitter and MySpace.
So many people are turning off social network sites that new internet applications have sprung up to help them. The apps automatically delete private content, friends and pictures and make accounts inaccessible with password changes.
Austrian psychologists led by Dr Stefan Stieger, from the Univesity of Vienna, compared Facebook users and Facebook quitters to see how they differed.