Back in January 2009, Facebook announced that they have reached 150 million users. The number was very high but it still lagged behind MySpace. But in early April, Facebook reached 200 million and it looked to us that the service might reach 300-350 million users by years’ end – and exactly that happened.
Facebook kicked 350 million users and while mainstream media started to hype up the whole Facebook vs. Twitter debate and how Twitter could turn into a threat for Facebook, this social networking service was acquiring millions of users. The fact of the matter is that the networks are complementary and with Facebook streamlining some of its features will bring forward simplification of Facebook in the same way as Twitter needs to "grow up" and become a platform that can actually make some money [instead of different companies using Twitter as their platform to earn $$$].
In any case, Facebook is the 800-pound gorilla in the world of social networks and from the looks of it will stay like that for a very long period of time. After all, 350 million people is more than combined population of United States and Canada… there is no telling when this user gain will actually stop or slow down. Judging by the rate, Facebook might reach half a billion users before the summer of 2010.