Sorry, as usual I was generalizing too much :-) I didn't actually mean to say that everybody has to belong to a group. I was thinking specifically about this one person, and musing over the difference between having close friends, casual friends, and just loosely belonging to a social group, even one that doesn't necessarily like you, but where you at least have a defined place.

Ach, I was going to write more but it's really hard to make sensible sentences today. It just makes sense in my head :-P