I'm of the mindset that if it is purchasable now it shouldn't be allowed. ie. No old games that are on PSN, XBLA, VC, GOG, or Steam.
I still agree with Xalphenos, along with our current piracy policy. It, along with the rest of our policies are still very much open to discussion though. Kind of like a "How are we driving? xxx-xxxx" or even a sort of board meeting type deal. We're certainly open to suggestions and improvements.