I just listened to the new Major Nelson podcast, and he alleviated a lot of concerns I had
You can -still buy the games-, but they won't be publically available.
What you have to do now, is find someone who bought that game, and have them use the "Tell A Friend" feature, which gets sent to you - and from there, you can try the demo, or buy the game.
The games -will still be on the server/service- but just not cluttering the shelves.
Obviously this can easily be alleviated by setting up another section of XBLA for these "bad" games and making the high-sellers and popular titles their own, but Microsoft obviously has enough trouble making good decisions as it is.