@Truthy I somewhat agree with @Johncdvorak on that. I wouldn't say _every_ online social community, but a good percentage. If I had to guess it is usually something like
1) they come due to the topic (show/programming language/hobby/game/etc)
2) they get attached to the community here at least at a semi-personal level
3) something about topic eventually upsets them/gets old/they find a new thing/etc
(1/2)