I notice the hiss when I have the head set plugged in and I am listening to music, I hear it in between the tracks. I thought maybe it was from the crappy head phones but I could be wrong; maybe RIM used cheap leaky parts in their Bold to save costs!?

A.

Update:
Actually it could be something in the software maybe because I just noticed if I stop the music I do hear the hiss noise for a couple of seconds and then it goes away.