It's not a lack of horsepower. It's an infuriating artificial restriction against running 64-bit Darwin kernels on 32-bit EFI. There's no technical reason why a 64-bit kernel can't be launched by a 32-bit EFI, but for some reason Apple has decided that 64-bit kernels will only boot from 64-bit EFI, and Mountain Lion will ship with a 64-bit kernel.

See http://netkas.org/?p=830 for more.

edit: Oh, and as to your whitelist/blacklist point - yes, Mac OS X checks what systems it can be installed on by Board IDs stored in "InstallableMachines.plist," not by enumerating the hardware.