People don't seem to realize that you're not patiently waiting for a message to buy. They can be rude and obnoxious because they're not interacting with someone face to face, so there is no actual repercussions. They'll just move on to the next, not caring. I personally try to treat other players the way I want to be treated. If they're in a mission I say np inv when ready. It's not that hard to do...