I love passing by live music or even recorded music while I am running--either in a race or on a training run--but I find the headphone thing to be both disturbing and dangerous. Several times while driving I have nearly run over idiots who ran (or biked) across a road way, not in a crosswalk, totally oblivious that they were risking their life (and terrible grief for the person who would hit them). For me so much of running is a form of intense concentration, a time to focus upon the act of running. Music from headphones just seems to take me out of my body, to lessen that focus. I respect that this could be different for others. Another thing about head phones that bothers me is how anti-social they are. I like saying hi to people, or nodding to a stranger. It seems sort of sad to me when I pass drones with headphones on who never acknowledge other people. Granted, not everyone who uses headphones behaves this way, but most do. And then there is my friend who I waited two hours to cheer on at Boston, who just ran right past me, wearing head phones, unable to hear me calling her name. Grrrrrr.