I just wondered this, as I'm always listening to music on Grooveshark on my phone which is of course a streaming music service, plus I'll be net surfing which of course is a fair amount of 3G data. I was concerned as to whether my phone might be using the earphones as an aerial/antenna, and therefore chucking out waves right next to my ears!
I could be totally off, I just heard that at least some phones did this with hands-frees?
Anyway, be good to have a discussion on this as mobile phone music services are of course becoming more and more popular.
In my case my phone is a Samsung Galaxy Portal running Android :)