My last year of college, I roomed with two guys I knew.
One was really laid back, the other was laid back but liked to argue (he was studying to be a lawyer). He really liked to win arguments, so sometimes we would discuss trivial stuff, but I guess that is what will make him a good trial lawyer. I tended to "agree to disagree" when he couldn't convince me (example, I liked a movie and he wouldn't), he liked to convince you, so I guess it annoyed him a little. BTW, in that instance, he had really good points, I just seemed to like the movie a little more (what can you do). They were both really good guys that I respected a lot.
Mid-year they both graduate, but one was planning to stay. On the way back from his hometown his car broke down and he couldn't come back. I couldn't afford to pay for the whole apartment, so I caleld him up so we could work something out (I was willing to pay for most of it if he could just cover what I couldn't pay on his side of the rent). He ended up saying he would still pay for his share in full. Felt bad, but there was nothing I could do about it. It seemed he slightly resented the fact that he paid, because he stopped talking to me.

Plus, all the annoying "discussions" we had probably stretched our friendship a little too much.