When you talk about the big social networking sites prevalent today, a lot of emphasis is often put on the sheer number of users these sites cater to. MySpace and Facebook, for instance, have a collective user base that well exceeds 300 million. Normally, you'd think of those figures as having a slow but steady climb. Unfortunately for Twitter, an up and comer in terms of subscribers, they are facing the exact opposite.

It seems that Twitter is a service many people respond to, at least initially. New subscribers sign up at record speeds, only to disappear the following month. At its worst, it seems Twitter was losing 70% of their new users after the first month. Having improved somewhat this year, they still face a problem of 60% loss on new accounts. A representative for the research company Nielsen posted some interesting statistics that show very volatile growth for the service compared to its rivals.

Though the user base is still growing as a whole, the concern is that eventually all new users will be exhausted and growth will halt, or even worse, reverse. The simplicity of Twitter makes it easy for people to get into. At the same time, however, does the service offer enough to keep people around or is it more of a novelty that quickly wears off?