Someone trying to do damage writes a virus for that device. there is not much desire to damage a device (Macintosh operating system) that is not popular enough to have an effect on most people and businesses. likewise it’s not very profitable to make software for such machines either. most of the computers on the planet have some form of windows operating system so most programs and viruses are made for them. with the Huge popularity of the ipod i see a multitude of nasty little viruses worms and Trojans in there future.