id Software's John Carmack made a brief post to a thread on Slashdot called "Copyrant" about software security. Carmack talks about the state of CD-Keys in Quake III Arena, dispelling the myth that there are working key generators, and mentioning that they plan on removing the lock on single player games that requires the game CD to be in the drive. Here's his post:

The "key generators" are all fakes. Some of them look like they work for a while because servers you have visited with a valid key keep a cache to let you in again.

As far as we know, there are no real key generators. If there were, we would have much more significant support issues.

We certainly will drop the CD-in-the-drive-for-single-player check in a future patch, that is our standard procedure after a game's primary sales are over.