Wow! Thanks for all the responses, and so quickly too.
To answer a question, no, I'm not in the process of running a game. I play in one, but was thinking about giving a shot at DMing in the future.
The thing that got me thinking about this was the thread on having two groups, combined with a healthy dose of fantasy reading.
My thought was, why not have a good roleplay game with two groups, each of which is convinced the other is some powerful force for evil, each working for their own diety (opposites of course). But I wouldn't want the players to know which side is the "objectively" good side, or even if I'll have an objectively good side. Obviously, this wouldn't work if one group had all evil alignments.
But I guess that's the beauty of DnD. The PHB and DMG are just suggestions and the DM can do whatever s/he wants.
Thanks again, and I hope the thread continues.
Alan
Also, if anyone who's running a game or about to start one would like to try this idea, I'd love to hear how it goes.