One plus mention by Sony of PS3 not having BC is the system produces less heat. Less heat could add more time to a system so in the long run it could be smarter to buy a 40 gb then a PS2 separate (just a little more here in US than a 80gb). For me now PS3 is just too expensive to run ps2/ps games which adds wear and tear to the system.
I sure most are clueless that the 80gb runs hotter than the 40gb as well.