I agree that speaking to someone concerning the grind spot does solve problems occasionally. Since you've set this standard of speaking to you before ganking you for others, do you hold yourself to the same standard of speaking to them before trying to insert yourself into an occupied grind area? Do you announce yourself to them or do you simply start attacking mobs and ignore the fact that another player is present? If you do these things, and feel that it contributes toward "proving" a logical argument about karmabombing, have you considered that most players don't do this? There are some people that will decline partying (also by responding in chat, so it's not just rejecting invites), ignore being asked to leave when a full party is grinding, and/or just try hit mobs as the player/party does when they respawn. They won't receive much experience, but they will disrupt the efficiency of the other player(s) present. I've actually had people doing this brag about how their guild "isn't ready for war" and that they "have more tears than you have karma."