A lot of people think of Facebook simply as a platform for people to stay connected and updated with friends (and enemies). It is much more than that, however, as more and more apps are being added. The main objective that the developers of Facebook are after is for users to spend as much time on this site as possible. The introduction of Facebook games is one way to do this. This is why we see a whole bunch of Facebook addictive games that people like you and me spend hours on end playing.
Facebook lets anyone and everyone develop apps and games that can be fully integrated with the website for users to play around with. Some of the most popular games in the world rank among the top Facebook games as the developers released official Facebook versions of those games. For example, Angry Birds Friends, which has been among the most played smartphone games of recent times, is one of the most played Facebook games.
So the next time you get bored of Facebook, think about all the Facebook games that you can play and you are guaranteed to extend that session by a couple of hours.