At first I thought this Phenomena only existed with obnoxious little shits at the back of the bus playing bollocks to their friends, but quite a few times I've seen (reasonably) sane looking people on their own at bus stops and the like playing "RnB" or whatever through their phones, as if it's perfectly normal thing to do.
There's a mental guy who used to get on my bus in Lewisham with a boom box playing Reggae and singing along. Everyone moved AWAY from him. At least he played decent music. Why are these people considered normal? Shouldn't we stare at them till they turn it off? (that's what I do)