Yeah, games are definetively moving towards new business-models. That can be both good and bad, but when it comes to the whole used-game issue, I don't really find it that big of a deal. Yes, it'd suck if we could no longer go to Gamestop and buy a used game for a little less, and heck, that'd also suck a whole lot for Gamestop considering used sales is their primary source of income. Though Gamestop has way too much power in this industry at the moment, and something like this would have a big impact on their position. Which could be a very good thing. Gamestop is the only reason we've seen shit like online passes and so on. The only reason.
Now, that said... online passes is not new. It is in fact a concept much older than most people might think. For years PC gamers have been forced to input serial keys in order to play their games - this is exactly what the online pass is, though I believe it was first put in place to combat piracy, rather than used sales. It achieves the same effect though, and you don't see PC-gamers bitching.
Should they bitch, though? Perhaps, but I do think that the system has worked well for the most part, even though it is annoying having to enter a long-ass serial key just to install your game. Microsoft has yet to really release any proper details about this, and a lot of what people are running around bitching about is stuff that's more or less unconfirmed. My point being; we don't know what they're going to be doing yet, though it seems clear that they are putting in some sort of restriction.
This is pure speculation, but I'm thinking they're gonna have a system where if you want to sell your game at Gamestop, the game will have to be deactivated from your account, and once you're in the store, the guys behind the counter would run the disc through a system that 'resets' it as a new game. This would probably involve a fee that Gamestop would have to pay to either Microsoft or the developer/publisher, so that they too get a cut. Because I do think that is all they want - I don't think Microsoft really wants to make it so that you can't borrow a copy from your friend or whatever.
Basically, I think this whole restriction-thing is something that's put in place in order to combat used game-sales, and hopefully it won't affect the consumer too much, or preferably at all. At the same time, I'm open to new ideas of distribution and business-models, so I'm looking forward to hearing the facts once Microsoft holds their E3 conference. I can't say I'm not skeptical, because I am. But yeah, I'm keeping an open mind for now, because at this point we don't actually know if we're going to get screwed or not.

