Maybe you are the bad room mate. :P
+1 for stealing my answer. Great minds.... :D
I had a female roommate and we never had a single fight.
Guess I'm the exception.
That's luck right there! The guys I've lived with have just been fat lazy otaku types, who are at least friendly and agreeable when you're cleaning up after them. The women I've lived with have been wombats.
I've had decent couch-crashers, but there's a peculiar phenomenon wherein anybody who lives in your living room, even if it's rentfree, will ultimately think that because their room is the central hub, it must be their house.
And you're invading their privacy if you pass through to the kitchen or bathroom.
"What the hell are you doing in my room?"
"What the hell are you doing in my house?"