6. Clan Ambushing
If I enter a server in an FPS and it's full of opposing players bearing the same clan tag, I will almost certainly always leave the lobby before the match starts, because playing against a clan, unless you're also in one, just isn't very much fun. I groan every time I see a clan "gatecrashing" a regular server, because it means that their superior tactical cohesiveness is going to result in them wiping the floor with the randomly-teamed together rabble that I'm a part of. It's not enjoyable - it's just frustrating. Perhaps that makes me sound like a sore loser - and that's probably not far wrong - and I appreciate that clans need to practice, but can't they do so on their own, private servers (assuming they have enough players)? To inflict it upon the public is just irritating, though I suppose that's a large part of the appeal...