I can't help thinking that our annoyance at people who sing their bit but don't listen to ours (yes, I feel it too) speaks volumes - or at least essays - about our own egos and desire to be applauded. I think it's probably not actually rude, really, it just hurts a bit if you're not too sure of how much your contribution is valued.

Having said that, I do think that sticking around is a better way to learn the singing, and the being together, that are part of the folk scene. I think anyone that clears off as soon as their set is over is robbing themselves and also taking something away from the scene itself that their presence would have added.