I also know a good number of current and former servicepeople online who've said their units had written up Zombie Defense scenarios/plans in their spare time. It's hardly surprising that when you get a bunch of intelligent, well-trained combat-minded people with access to significant quantities of weaponry together for long periods of inactivity broken at irregular intervals by actual danger (if in a combat zone) or regular intervals of tedium (in a non-combat area), they'll end up with contingency plans for everything, up to and including zombies uprisings and alien invasions.
But more importantly, zombies are inherently problematic as a threat from another angle, which is competing against themselves. I think I originally got this from Cracked, but it's a salient point regardless - a zombie's sole food source (people) is also its primary means of reproduction (people), which is also its apex predator (people). It's like having to wrestle a lion into submission bare-handed any time you want to have sex or make a sandwich.
That said...any story featuring zombies, or a zombie apocalypse that succeeds in destroying society as opposed to simply crippling it, has to take all of that above and basically handwave it to get to the meat of the story, focusing on the survivors and how they make their way through a ruined world. The zombies are like the aforementioned volcano, just a backdrop element that occasionally tries to eat you. Similarly, enjoying a zombie story requires accepting that handwave into your suspension of disbelief, otherwise it'll just eat at you and ruin the fun.