I think social media is something that will inevitably have a cycle of growth and collapse. Small groups tend to attract a more creative people that want to make something new. When they are successful that attracts lots of other users and the groups grow. Once they reach a certain size the nature of the group inevitably changes. Maintenance starts to overtake creating, and as it gets bigger the content becomes primarily quick & easy content and things created by those with vested interests (advertisers etc). At that point the type of person who created the initial small site tend to be looking for somewhere else where they have room to create, and the content on the large site becomes more and more recycled content and advertising. Which means the users start to look around for something different - and find some of the things the people who have left earlier have started to create. At which point the cycle starts again.