I put:
Maybe
Yes
Depends
I think in your situation, with the guy being a young kid with bluetooth, I am leaning towards saying something. Then again, I'm Russian, and was raised to just mind my damn business in situations like this, because it's not worth getting stabbed over some BS.
I put Yes, because if you do decide to say something, you are basically committed, and gotta go all the way. You can't just shut up, I'd holler at this guy until he went back to the end of the line, or until everyone paid attention and saw what kind of a douchebag he is.
Finally, Depends also rests on how big he is, how much of a hurry I'm in, how cold it is, and other factors like that.
There's always a chance it ends like this:
http://www.youtube.com/watch?v=IgzrJAgegKE
Oh, and yeah right @ 70% of people saying something.