El_Caz: The point of reselling something is that you lose your product and get money instead. How do you sell a digital product that can be copied and recopied for back up purposes or whatever? Unless you're talking account numbers for multiplayer games of some sort, I really don't see how they'll be able to implement reselling and what good will it do a digital company to do so.
Only way I see it is with a permanent connection online and getting keys with your new games, forcing you to register in order to play it. Resell the game, lose your key and you can no longer play your game, no matter if you reinstall it.
It's not so much re-selling as returning your activation key to the store for credit towards other games. If they have the re-selling process connected to the game's uninstall routine, then you don't need a permanent internet connection to play the game, you just need an active one when you install/uninstall it.