Potential Problems of Community Sites
From unmediated: When the value of a website is completely dependent upon the participation of its user community, changes made to the site that upset that community can have a very negative affect on the website.
From the full article:
...the relationship between users and empty vessel web services [i.e. flickr, Facebook, YouTube]is unique in the history of user/technology relationships — and user/media relationships, for that matter... The sense of ownership is now just based on use — it’s based on the users’ content actually bringing the service to life. So while Flickr, Facebook, and YouTube, as traditional corporate owners of the service, can technically do anything they want — and they will surely have valid business reasons for wanting to make changes — they are ultimately beholden to their users.
Just ask Friendster.