Ok lets put in another factor, In the UK, if you were on public transport listening to music using anything other than earbuds headphones, you're a target for getting robbed. People wear discrete headphones here, because if you make it known you are listening to music, you're likely to have a phone or mp3 player on you, making you a potential victim. This is how it is where I live, and in London (you could probably get away with it in Central London), and definately in areas like Birmingham, Mancheste, Liverpool or Newcastle.
I bet American kids walk around with iPods in their hands or hanging around their necks on the outside of clothing. Here thats an open invitation to getting jacked.