Is co-op only fun with friends?

Every time I think of co-op, it seems to me that it'd only be fun in an organised fashion with people that you know.

Sort of like "hey lets finish this game this afternoon" kind of thing. On the other hand playing with randoms, you could get people dropping in and out all over the place, rendering the whole experience kind of impersonal and pointless. Am I right?

@thereal25: I was recently wondering this myself. I guess if you find some decent co-op partners who want to play the game properly and have chat headsets then it wouldn't be too bad.

But if your real life friends are up for playing the same games as you then that's obviously the best way to go. Sadly my friends aren't really gamers, they only play FIFA.

Co-op is definitely tends to be more fun when your with people your familiar with, but I've had just as much as fun playing with randoms.

Alright. I should give it a try. Now I just need to find a suitable game for it!

It just doesn't seem appropriate for Borderlands 2 somehow. Probably because it's such a big game.