Inviting someone to group for the purpose of killing them, is about the lowest thing I can think of. To me, what it really means is one of two things - either the player doing that is so shitty that it is the only way they can kill anybody, or that pk count is the only thing important to the player and it doesn't matter how they get them. It's like grouping for the purpose of hunting and ganging down anyone in your path only lamer.