AIBU can be very annoying. I sometimes post on them but rarely say YABU or YANBU because it annoys me.
I can't see any harm in groups really, even if they do seem gang-like, I don't see how that can be avoided when people have known each other a long time. I can see what you mean though, Aitch, about posting generally on the board. Sometimes it's easy to flick through and then just say hi to the people you know. Laziness maybe.
And not everyone is nice on 10/10. I for one am quite prickly.