My major issue with social networking sites is that when the fad for one passes, you have to rebuild your network on the next one.

I have also seen many apps which relied on some social parts but for which you have to build your network again.

So, I really like this since it allows one to develop a social app without having to manage the social network part. You have to admit that Facebook has been doing a great job at making their network prevalent and ubiquitous. Which is kind of worrying I suppose.