The big guys know they can't do it all and so they go to Application Service Providers to give them what they want. Long, long time ago, I worked with a company that did the same for community solutions -- message boards, instant messaging and chat. our clients were MTV, Oracle, VH1, CBS, GE and many more.
My point is, I'm beginning to feel that this is a very good idea that needs to be approached with sophistication.
You will be known as Social Network Solution Providers.