I'm really just nitpicking btw. Walking Dead is presently the only show I find to be worth watching. I enjoy the action, the drama, and of course the zombies
That said, I've noticed another flaw (not counting the undead walking around) over the last couple episodes. They're collecting gas they come across, Daryl switches out a battery and gets a car buried in bushes running quite easily after who knows how long, Carol takes that car in the suburbs and it starts right up...
The zombie apocalypse started what... a year ago give or take a month? Highly refined petroleum products, such as the gasoline in cars, begin to break down fairly quickly if there isn't some type of stabilizer mixed in. I only know a few rednecks or car nerds that actually do this. The other 99% of the population just pumps it and drives til it's gone. In that state, left to sit, gas would be pretty much unusable in a few months.
So if any of you find yourself in a world full of zombies, don't plan on having reliable vehicles a year after civilization ends unless you had the foresight to stockpile a bunch of gas and mix in a stabilizer, in which case it might last for a couple years. Even then, it would still eventually go bad.