everything on PSP runs over instructions, such as spin, stop, eject, etc...
anything with instructions, although not necesarrily destructing, it can still be in form of a virus.
someone said above, what fun is it to damage peoples' stuff, well, how do you think antivirus s/w developers survive? If their s/w was the best out there, it is thanks to the virus developers. Still to some point same people as antivirus s/w makers.
Even the doctors won't heal you @ the same visit and will ask for follow ups,

don't get me wrong, but that's the way, people has to survive. Dentists, if there was no tooth decay, what will all those dentists do?
