Why not a allow us the digital versions of games when we get the game. The code shouldn't expire, and be included within the disc. (think digital manual).
Since you have to be online to redeem the code anyway, if someone else redeems it, the digital version wont work anymore. This assumes you gave the game away. That way, you can loan your games out, and you still have access. When a game is sold back to the store, that store should be able to enter that code from the disc onto a master account.
That way, if you sell the game, you wont get lucky if someone who picks it up next doesn't have internet. Or, the game is never actually resold again.
Every problem is solved, and you can still loan your games to your friends... WHILE THEN STILL HAVING ACCESS TO THE DIGITAL VERSION, MIND YOU! IT'S GENIUS!
Just don't let your friend sell your disc, or enter your code, and you're good.
And, there might be a minor way to get around this, but nothing can ever be 100% fool proof when it comes to something like this.
