@SamuelRSmith
True say. But I don't think you will have ads on xbox live saying "Used games section". Also I doubt someone in the buy/sell section of craigslist will waste time to sell a 4 dollar game. So they won't be easy to find at all if someone wants to buy used.
But if you want to sell something to a freind or trade, I think it benefits MS/Sony/Nintendo to add 100 points to the transaction rather than see it happen the illegal way and not get anything.
To do this there obviously needs to be a secure network like xbox live... since I can play any wiiware game i want without modding my system for free, that wouldnt work...obviously someone could just re-sell the game over and over if they could copy it.