According to Phil Harrison, the system allows gamers to buy and sell used games, but prevents multiple owners of a disc.
Harrison explained, "So, think about how you use a disc that you own of an Xbox 360 game. If I buy the disc from a store, I use that disc in my machine, I can give that disc to my son and he can play it on his 360 in his room. We both can't play at the same time, but the disc is the key to playing. I can go round to your house and give you that disc and you can play on that game as well.
"What we're doing with the digital permissions that we have for Xbox One is no different to that. If I am playing on that disc, which is installed to the hard drive on my Xbox One, everybody in my household who has permission to use my Xbox One can use that piece of content. I can give that piece of content to my son and he can play it on the same system."
If you play the game outside of the house on a friend's Xbox One, you must play under your own account. If he wants to play it under his account, he must pay a fee? Why? To prevent multiple ownership of a single game.
However, if a gamer wants to sell his game, it has to be registered. "We will have a system where you can take that digital content and trade a previously played game at a retail store," Harrison described. "We're not announcing the details of that today, but we will have announced in due course."
This may be the chief reason all games have a mandatory install and be able to log in with Xbox Live - removal of the installation would tell Microsoft that you no longer own the game and it can be sold at a retailer, who presumably would somehow let Microsoft know they have the disc.
Confusing, but hopefully this means gamers can still rent and buy used games on the Xbox One.