Yeah, I thought of that too. If that were the case wouldn't they just need to verify that it's a music player only (and ban phone ear pieces)?
Most of the time I don't use it either. Usually, I like to be social and pay attention to what players are saying. This particular table wasn't talking much so I decided to jam out. It really helps me focus and have a better mindset. The only thing I worry about is how it affects my table image (and how people play against me).
Some people seem to believe that having headphones on makes you an "internet punk". IMO, guys wearing shades at a 4/8 limit table look worse than people with an IPOD lol.
I haven't been able to find out much about the rule yet. I'm surprised our buddy Fred hasn't jumped in on this one.