>It boggles the mind why not in a single one of the zombie stories out there nobody bothered to wonder where the zombies get the energy? The way most of them work it's like cold fusion landing in one's lap.

Zombies, like vampires in the pre-industrial age, are meant to represent the horrors that lurk beyond the limits of human understanding and control. Although I'm sure some author has attempted to "harden" zombies like that, to me the more you try to explain them, the less effective they are as monsters. Because they don't work rationally, they're demons of the Id.