I even recently "participated" in a conference call using my iPhone for about an hour. It was one of those situations in which I didn't have to interact...just listen. (It was also incredibly boring.) In general, I sometimes ride while listening to an iPod/iPhone/whatever. However, I only turn up the music to the point at which I can rub my fingers together in front of my face an still hear the sound of them rubbing together over the music. Much louder than that and I feel like I'm missing out on the sound around me.

My other thought, however; has often been. Am I really agile enough and is my hearing so incredibly astute that hearing a car as it barrels down on me makes any difference in my likely survival? I really doubt it.