the community is dying
It's not that.
If you lock people up in a room long enough, no matter how much they like each other, they'll start finding stupid things to argue about.
The trend I've noticed is that after people have been here for a year or so, they start thinking about leaving. Usually a mixture of "well the people who I played with aren't here anymore", "it's just not the same", and other variants cause people to feel that the community is dying/going to shit/etc.
I kind of went through that phase a while back, but you either accept that things change, or move on.
Anyways, I kind of drifted off there.
tl;dr Tension.
//edit
Okay, fuck you Deacon for beating me to it. ;_;