could it work? (Score 5)

There are two issues here:

1. could they block alternative client tools?
2. could they keep people from removing the protection?

the answer to 1. is probably. Certainly they could sue anybody who is distributing alternative client tools ala deCSS and keep those tools out of the hands of most users. They could also have some kind of access mechanism that would change every couple of weeks that would be transparent to end users who would get automatic client updates to be able to use the new access mechanisms. Thus a determined hacker could get through the protection, but they would have to do it again every couple of weeks and couldn't reasonably distribute the hack to a wide enough user community to pose a threat to napster.

the answer to 2. is less clear. Obviously they couldn't change the way you access older napster files on your computer. They could encrypt them, which isn't terribly feasible in terms of having to be decrypted for every playback unless the encryption is weak (maybe I am wrong on this). What about having a funky scrambled format that changed regularly? then anyone cracking it would again have to distribute updates through illegal means, which is slow, whereas their software could remember the old formats and descramble based on the date of the file.

I guess my point is that they don't have make it impossible to decrypt mp3 files to win. They just have to make it impractical for users to do it on a wide scale.