OK, then sure. I just mentioned that because I let a guy play a warlock once and was completely surprised when he insisted that he had to be evil and the class was based around serving a demon lord. Naturally, I didn't think that goal would sit well with the rest of the party.
As I've said, I'm not familiar with all the extra splatbooks and don't have time to read them all, so don't be surprised if I ask how something works.
As an aside, and not directed at anyone on FSTDT, I've found that in every gaming group I've DM'd, there's usually been at least one guy with a laptop full of pirated PDFs who assumes I'm familiar with every sourcebook in existence and that every race/class/creature ever created exists in my campaign world somewhere.