@rye256: Yeah, lending, renting, gifting are on the line here. Trading and selling might be affected to some degree as well. Microsoft won't say what they're poking and prodding at there.
A solution for lending/gifting would be to give them the game and your login details. It is a pretty shitty solution. I assume the minute you log in they'll get logged out and vice versa. Also bad security practice.
Really, really hope Sony isn't going down this route too.