kind of like how you can't run unsigned executables off of the xbox, right? ;P
just because the default UI is incapable of doing this doesn't mean there isn't a potential overrun exploit where there is no signature checking.
anywho.. good conversation folks. That is a good point on different kinds of piracy and wanting to stop certain kinds. though suprnova at it's peak saw something like 4000 simultaneous downloads of popular ps2 games.. certainly sony has to balk at that to a degree, even if it is mainly worried about bootlegs.