Basically the only aspects that differentiate a social network from a more traditional community (forums, message boards etc) are Profile pages and Friends.
Is this distillation correct?
And if it is, are profile pages and friends really necessary for the uwebd community? Because I have seen a lot of quite successful online communities that did not have either.
In fact, a little off topic, but a social network actually hurts community, instead of helping it, because it is a crutch. If you need a computer to help you remember who your friends are, then are they really your friends?