I hate it when such things happens...
why doesn't it come to some people that it's nicer to ask if one can join the party then attack? :S
It really ruins the whole thing. I hate it when they just attack straight away, then ask to be partied up. Then what happens is...even if I was considering to let them join me, I would just refuse.

It's even worse when you don't get the kill.
Some people are just jerks.