Sony's system avoided those concerns by limiting the total number of consoles a given account could authorize, and requiring a system to be brought online for the de-authorization process. So the authorization token can't be passed to a new holder until the old holder gives it up. Similarly, I would need to sign in to PSN and transfer my claim to the license to you, and then you would need to sign in to authorize your devices to make use of it.
So all of the license management can be done this way, it seems. If you want to decouple the license from the disc, you can do it in exactly the same way. It won't require periodic checkins, but it will require a connection for license (de)authorization, which still puts it out of the reach of a significant number of console customers, I suspect. So I don't know if we're quite ready to completely decouple like PC has done, but we're probably getting close.
In the mean time, I don't see any significant obstacles to the transfer of digital-only licenses, apart from the creators' understandable reluctance to allow it.
Yeah, I agree that if we're talking strictly person to person, or digital-only license transfers, there's no need for periodic checks. It just gets a little weird when a 3rd party intermediary that you visit in the real world, and not on the internet (like a retailer you trade your disc into) has to get involved.
If Person A trades a disc to Gamestop, and Person B buys that disc, Person B is obviously gonna expect that disc to work when they get home. Gamestop connects to Microsoft at the time of the trade-in, deauthorizes the license, and then Person B connects to the internet once to gain authorization when they get home. Person A is out of the picture, and they can abuse the system and keep playing the game by never connecting. If Person B got a message saying "sorry, Person A needs to deauthorize this, until then your game can't work", that'd kinda suck, lol.
But then it'd be funny if Person B goes back to Gamestop, gets a refund for the "used" game, and then Gamestop gets the license deauthorized. Now as long as both Person A and Person B never go online with their console again, they both technically still have a working copy of the game without actually paying for it, lol. Some friends could probably work out a scheme to abuse this system (though like I said, I wonder how many people would actually try to do all this just for the sake of free games)
As I'm typing all this out, the funny thing to me is that for all the talk of "MS wanted to kill used games!" the sole purpose of the 24hr check was just to appease used game/trade-in retailers like Gamestop. If they avoided that whole scenario (like all the other "fully digital" ecosystems), they would've never needed the 24hr check. But then Gamestop and publishers would probably be pissed, like you implied.
Also under this model (no periodic checks, closer to Steam), the mainstream console consumer would probably be weirded out by the fact they couldn't trade in their game to Gamestop anymore.
Dean Takahashi needs to write a book about all the negotiations and shit that went into this, heh.