Twitter's user growth is tapering off alarmingly quickly. With an active user base of now 255 million monthly active users
, the apparent deceleration of Twitter’s growth suggests that the service will have a very hard time coming close to Facebook
’s user base, let alone matching it. When Facebook's growth rate first dropped to the level where Twitter's currently is (25%), Facebook already had 800 million users. When Mark Zuckerberg was asked why his company
had acquired WhatsApp
for $19 billion, he replied that services whith the potential to reach a billion users are hard to come by. It seems like Twitter isn't one of them.