In any zombie story you're going to have to go with a little suspesion of disbelief, or else give the zombies or its cause some extraordinary powers.
The problem I see with a lot of these thread is that people have seen too many movies. They expect that if the dead started to rise, they'd suddenly turn into John Rambo: Zombie Killer. When in fact, most people would hesitate, get frightened, or freak out completely when faced with a horde of partly decayed creatures covered in blood and gory wounds. And probably smelling to high heaven too.
Actually if you're interested in this sort of thing, I'd suggest tracking down a copy of the Zombie Combat Manual http://www.amazon.com/Zombie-Combat-...1775053&sr=1-1
It really is a well done and researched book rather than a quicky knock-off of Max Brooks' book.
* I can see how zombies could be easy to defeat if it occured in pockets that could be isolated and held in check. But if it occurred everywhere at the same time?
* In some ways, fighting zombies is easier. They don't shoot back, or really have any real weapons apart from their bare hands. Otoh, theres no such thing as a wounded zombie. Shoot a human opponent in an arm, leg, or chest, and they're pretty much down for the count. Humans can also be intimidated, or knocked out by concussion weapons, flash-bangs, or shrapnel. The same shot will only slow a zombie down for a few seconds. (another reason I also really recomend anyone track down a copy of WWZ. It really does cover a lot of this stuff in detail)
* And yes, many people have guns. But how many, apart from a few 'gun nuts' have more than a few boxes of anno lying around? That plus the fact that unless you're a hardcore gang-banger, or combat vet, you're likely to have a problem with, or even hesitate to shoot anther person. No matter how bad-ass you think you might be.
Theres also the problem that, despite what we see in the show, making consistant head shots isn't that easy, unless you're right up in the zombies face.
Just my $.02.