It's a shame there is so much uncertainty around rights management this time around. While the goal of allowing a user to install their games library to the hard drive and never have to swap discs is laudable, it seems to have come with a very significant downside now that you can't just rely on "disc in drive = YES" to validate ownership.
It still seems to me there should be ways to get the benefits of no disc swapping while still not complicating used games/sharing between multiple boxes in a household/lending to a friend. Then again, as I think through various options, I can always find holes in them. The closest (but still imperfect) to that would be serializing each disc/install (practical?).
Supposing the plan is indeed to use an activation code of some sort, then it seems like it should be possible to serialize discs by printing this code right on them. It could also be included on a paper insert in the case, for convenience's sake.
Joe purchases a game disc, pops it into his Xbox One and installs it/authorizes it over Xbox Live using the code. Joe later decides to lend the game to his buddy Bob. Bob pops in the disc and installs/authorizes it over Xbox Live using the same code -- Xbox Live know says "OK, this is Bob's game now, de-authorize Joe". Bob finishes the game and gives it back to Joe, and he re-authorizes it -- Xbox Live says "Joe now owns this game, de-authorize Bob." Joe's daughter Jane decides she'd like to play the game on her own Xbox One... Joe hands it over, she installs it using the code and ownership transfers again as before. Jane finishes the game, gives it back to Joe, and Joe sells it on to some guy named Chuck. Joe lost the paper insert with the code, but luckily Chuck can read it off the disc -- he installs the game, authorizes it, and ownership transfers again.
Provided the Xbox One performs a disc check every time authorization is attempted, this type of scenario should ensure that one and only one person can play any given copy of a game at one time, regardless of what Xbox One box or Xbox Live gamertag is being used. The disc check is essential, I think -- otherwise Joe could decide to be a jerk and re-authorize the game after he's sold it to Chuck, leading to an ownership tug-of-war. And I think having the code be printed, as permanently as possible, on the disc is also essential -- otherwise, Joe could sell Chuck the game and conveniently "forget" to include the authorization code.
I'm sure I've probably missed something, and there are holes that could even be poked in a scheme like this, though.