Really the last few comments have reminded me how much of mess alignments are and how it's usually best to ignore them unless your dealing with angels or demons and such extreme cases.  It's not terribly necessary in D&D beyond things like: The undead, fiends, outsiders, evil clerics, and certain spells.  On the more mortal level it just get's really muddy fast and the last few editions haven't really helped.  When it get's to that point it always sort of felt like it was kludged from a different system.