Thanks for the posts guys.
1) My fellow players and I have alot of fun with the honor systems. In a game with no alignment, it gives your character a set of morale guidlines he can follow...or break. How many times in DnD have you ever seen a DM enforce alignment? The honor code is a load of fun, especially when "civilized" characters run into barbaric savages. A bunch of great Roleplaying ensues.
As for thieves having honor, well we all know they dont. BUT, they do have functioning guilds. All those burglars, fences, woman stealers, second story men, and tomb raiders need a place where they can be relatively safe and be able to get rid of thier ill gotten gains. True there is no honor among thieves, but I'm looking for an honor system that would spring up inside a thieves guild. Look at Arejun. The Maul DEFINATELY has a code of conduct there. Potential empployers can hire just about any man they would need for the job, and know whomever they hired should be relatively discreet in the identity of thier employer. Without some type of thieve's code, the entire system would break down. There has to be some type of "civil agreement" in place amongst the thieveing community. Granted, you dont have to follow it, but its there for the more organized guilds.
De rote baron had some intresting ideas, I'm going to write something up and I'll post it here when I'm done.