Here's another interesting detail from the Xbox news that popped up this evening. Microsoft says that 10 of your "family" members can access your shared games library. Not just on your console. On any Xbox One.
Xbox One will enable new forms of access for families. Up to 10 members of your family can log in and play from your shared games library on any Xbox One. Just like today, a family member can play your copy of Forza Motorsport at a friend’s house. Only now, they will see not just Forza, but all of your shared games. You can always play your games, and any one of your family members can be playing from your shared library at a given time.
There's still some confusion here. Can Microsoft really distinguish between who is a cousin and who is just your old college roommate? Who knows. I imagine you could identify 10 "people" as your "family" members and get away with it. Kind of like how HBO Go and other premium streaming services work.
The other detail to note is the mention of a shared library. Presumably, you'd have a specific folder with specific games that people with access can play. Does that mean Microsoft can limit how many games you can physically include in that library? Probably. We don't know for sure just yet.