I'm one of those people. Granted I don't subject everyone around me to it, but I am one of those people that will listen to the same set of songs perpetually until I've memorized ever lyric, every last note. I'll listen to the same song for hours on end if it fits my mood, and I really don't think there's anything wrong with it so long as you use headphones and spare the ears of others.

The reason I do this is because sometimes I want one song and only one song floating in my subconcious, sometimes I forget I'm even listening to it.. sometimes I just need the stability it seems to create. I especially do this "listening to the same songs over and over" thing when I'm feeling any one emotion intensely. If I'm confused, hurt, sad, depressed, ecstatic, or feeling really dreamy I might listen to a set of songs repeatedly until they bore me or no longer fit my mood.

I guess some people are just freakish in this way, but it's not reason to be hostile or resentful.. just ask them to use headphones. If they won't, that's when you get to beat them over the head with a wet noodle.