On a PVP server, if you see horde surrounding an alliance person who's killed you, you think they're fighting and you'll have the upper hand.
So you go in and you attack, and you watch as the horde just stands there while you battle for your life.
And you think: WTF?!
(Or some nicer variation, like "What the Poo?")
We've discussed this from Alliance side, when a level 70 rogue refused to stop his friends from killing my group over and over again.
What is the etiquette when your friend on the other side is fighting in PvP? If you stay out of it, the horde gets ticked off. If you kill your friend, the friend gets ticked off.
Is logging the only acceptable response?
In my humble opinion, the proper response is stopping the fight and letting the people on your side know if you can't help them. If your friend refuses to stop, you kill them. If your faction refuses to stop, you leave them to their fate and possibly /ignore, based on how much of a jerk they are.
The worst situation, I think, is if the friend is a ganker whom the person attacking hates. If you don't ally yourself with your faction, why are you ON that faction? Switch, moron.
Thoughts? Personally, I've come up against this twice already, people not helping me fight folks who have, in the past, killed me unfairly, and I want to gouge out their eyeballs. I always /ignore b/c, really, anyone who allies themselves with a jerk ganker must be a jerk ganker themselves. And is therefore not worth my time.