Nope, not heard of this nor had any experience with it, and i force my n900 tripple rca to be used as a 3.5mm to dual audio rca out lol, that sends feedback back and forth, still no issues :')

This issue looks more like people playing with the output values and pushing them too high, i've had this happen once to my headphones on a mac (and it blew the left/right channels) but dont think n900 has the potential to do this!

Could be wrong! more worried about your iphone doing it then anything else, the apple experience eh.