Well I agree but, I find that a zombie apocolypse without any explanation as to how or why the zombies exist can be very frightning and entertaing [urlhttp://en.wikipedia.org/wiki/The_Walking_Dead[/url]
When you tack on well they exist because of pollution or some anger virus then that kind of kills the whole fear factor.
I'm sort of on the fence when it comes to having a "Kemmler" who directs the zombies. Now Jims book works very well, but I wouldn't consider that book a zombie novel. Even if there was a zombie book where the whole thing was focused on the zombies I still think that having a person controlling them overshadows the zombie horror and then it becomes not a zombie novel but a novel about a necromancer.
For me the horror in a good zombie story is the futility of it all. YOu don't know why the zombies are there, you dont know if they will ever go away, you don't know if you can ever be safe so it seems futile to even fight them or try to flee. It's the horror and thrill of desperation. For me if you add the controlling factor then you take all of that away. You know that guy made the zombies and you know that everything can go back to normal if you kill him. At that point it's not about the zombies or despertly trying to cling to life and civilization anymore. It's just about some hero(s) killing some villain.