as far as the law goes concerning earphones, i guess it may vary by state, but i know that in NY state you may only wear an earphone in 1 ear for it to be considered legal. i'm not going to say that i didn't break that law earlier today though...

and like others, i always use an iPod when i ride alone, and never when i ride with a group. i know someone that used to use one when he rode with groups, and was one of the most hated riders because of it. i personally find that disrespectful, because communication is very important when riding with a group...