Most missile-guidance systems have all the complexity of a Game Boy and the CPU power to match, that way they are absurdly reliable. So, in theory, I guess you could guide many, many missiles with a PS2.
I like the looks of all those PS3 rumblings, I'll have to pay attention in Computer Architecture and read up on parallel processing in my final years if I ever want to program well for one I reckon... IBMs involvment is also very heartening, I mean, they are experts in the field of parallel architecture, and this new Cell architecture stuff is most likely going to be useful for them in working out how to develop far faster CPUs that should hopefully give them a head start on their rivals...
As for the "oh no, more hype a la PS2" blahing- the old feller face that was shown off proir to PS2 release looked about as complex as the facial anims in SH3's cutscenes, the media and certain old biddies with no game experience to speak of (George Lucas, for example) spun the system specs wildly out of proportion, not Sony, as far as I'm aware (find me some quotes to prove me wrong, tho).