reading a disk in linux is easy, but getting the ps3 to play that image with it's real OS will be very hard I bet.
Sony have been fighting a running battle with the PSP scene since day one. I bet they really don't want a repeat of that. Letting linux be installed lets homebrewers have their fun. I find it hard to believe sony didn't know that dumping the contents of the blu-ray was possible. I bet they know, but are confident enough that the PS3's own OS can't be made to run the copy.
I will no doubt be eating my words given a few weeks/months