I listen to my iPod while riding sometimes. I don't know if you guys are aware, but iPods have an inbuilt speaker and you don't have to use ear buds at all. I just strap it to my forearm in an iPod arm band. The volume is low because the speaker is slightly covered in the arm band, so it can't be loud. Certainly loud enough for personal use though, but not enough to bother other people on the paved bike paths I ride.

I'd say that it is also not distracting me and perhaps even enhances my alertness as I use it when I get a little bored. Usually it is just there on my forearm doing nothing, until the last 30 minutes of a 2.5 hour ride, and I find this enlivens me. I generally (I'd say always, every time) hear bikers coming up behind me before they ring their bell to pass me. (I'm pretty new still and overweight, so I get passed a lot!) I have never gotten any surprises that I can recall because of the music being on. I can hear the birds and the creek, the sound of my tires on the pavement, and really everything imaginable quite well and it's a really nice experience. Riding with ear buds is unnecessary and I'd say extremely dangerous. I can only imagine why anyone would do that is that they assume that you need the ear buds for the device, but turns out you don't.