I just had an interesting theory about Dent, Maroni, and motives... it's probably not correct at all, in fact, I don't think it is, but it's interesting nonetheless.
The Joker takes over the mob--we know this. Now, with all of that political stuff that's going on between Joker, the Mob, Sal Maroni, Corrupt Cops, and Harvey Dent, it's probably safe to say that the mob is looking for whatever dirt on H.D. they can find. The Joker, however, being an anarchist, just wants to kill him and get it over with.
Now, suppose that the Mob finds something that puts a little stain in the White Knight's armor. It kind of breaks this savior picture the people have of him. Maybe it paints him an outright hypocrite. Or, it doesn't even really have to do with that--it just may be his association with Batman in private, and his public outspoken 'tude against him. In either case, Harvey Dent appears to be a two faced hypocrite.
Now, for the Mob, for Maroni, to just kill Dent would be compassionate, in comparison to this new info about him that tarnishes his record. So perhaps they set up the big scarring thing, where they set him down, half of his face first in some gasoline, pushes him against it, and lights it on fire...creating the Two-Face.
Then, it becomes a Scarlet Letter, basically. Then, not only does it set up some more interesting situations regarding Dent, but it also leads quite logically to his becoming a vigilante. That, of course, puts Batman into another rough dichotomy, or perhaps deeper into his current one, regarding his presence vs. his effect.
What do you guys think?