Digital rights management or something like that. I am not sure what the s is for.
I got burned by that crap bad with my Zune, I had a bunch of music but when I got a new computer it wouldn't transfer over because although I was signed into my account I didn't have the rights to posses it. The little indian chick on the helpline knew even less about what was going on than she did the English language. The whole thing was nothing but a PITA and I got nowhere.
Basically once you buy a game it is yours forever and you can never share or sell it. Which means you can also never buy a used game for a discounted price. Microsoft would have a complete monopoly on the market, you couldn't borrow a game from a friend, if you wanted to play it you would have to shell out whatever they think it is worth and hope you like it. To add insult to injury it is not backwards compatatable with the xbox or 360 games.
I am basically not seeing too much to really motivate me to replace my 360 for a while...