I don't think there are any computer viruses to date that were specifically designed to infect and damage iPods, and I don't really see how it could happen. Viruses work on the principle that whenever a binary (executable) file is executed, the OS will also execute the code of the virus so that the virus can cause damage and multiply. So far, viruses that infect non-executable (data, e.g. MP3 files) files are far more rare, as it is much harder. This is because it must take advantage of a specific bug or security hole in the application that reads the file, and thus, the rate of infection is low.
In the iPod, all the files that can be played are MPEG3 or AAC format. Unless the iPod's firmware has some huge hole in it that allows properly formatted audio files to execute arbitrary instructions on it, and someone decides to make a virus for it (however unlikely either of these events are) then we might have something to worry about.
The virus can "live" on the iPod, though, as the iPod itself can act like a hard disk, and if you save an infected file onto the iPod in HD mode, it cannot be used by the iPod, but will still be on the iPod, and may be able to infect computers that the iPod is attached to.
So, if you're concerned about damaging the iPod by accedently putting viruses onto it, it just won't happen, but don't sue me if it DOES indeed happen
