EVE Online not because you know your bosom buddy is waiting for you, but because flying in 0.0 is pretty dangerous on your own. So most of your friends in a game start off based on you deriving some benefit, and with a few exceptions that's where they remain. The problem comes when that benefit is outweighed by something else. That's when guilds of friends have nasty splits over what seem like minor matters, because someone crossed a line and no amount of in-game support is worth the drama.
Sometimes it's all game-related, and other times outside drama shoves its way into the game. Either way, it's something bad enough that you're often cutting off a significant advantage -- sometimes even a whole guild and the concurrent access to the endgame -- for purely personal reasons. Those of us who have done so, though, rarely look back with regret. What about you? When has a relationship in a game passed the point where the benefits are outweighed by the drawbacks? Or have you only ever been on the flipside of the equation?