How on earth did that get there?

Wow - piece of weird news of the day - there have been a couple recent (admittedly small scale - look here and here) instances of brand new mp3 players selling pre-loaded with, not new music, but viruses. How do you get a virus on a mp3 player straight from the factory? Is there an inside man or something in the factories loading this thing for the fun of it - how would it happen? If anyone has any ideas I'd be glad to hear them.