Since you bring up the question of culture, I think the show is trying to address a certain trend in contemporary American society. The main characters tend to be somewhat conservative in value, and the storyline works in topical themes such as gun ownership, property rights, religion, and certainly race. But the show also shows a certain discomfort with stereotypical shortcomings associated with the conservative movement: racism, close-mindedness, unthinking religiosity. So instead it opts for a multi-ethnic survival group even with interracial couple(s), and for a certain amount of skepticism towards religious fundamentalism if not towards religion. The biggest jerks are the two, urh, rustic brothers. The show certainly made effort to make race seem like not a problem except for the one bigot who made it a problem.

This does make me wonder what zombies represent. Does the show have political undertones? That is, are zombies those people who do not share moderate conservative values? Note that the group had to escape from the city to the country. Does that reflect the blue urban/red country divide in today's political landscape?

Now, don't get me wrong: I don't think The Walking Dead is some deep show. But often cultural forces work themselves into TV shows. It's just that the shows don't give a deep answer to our social problems.

On a separate topic, the end of Season 2 seems to set up two different modes of survival: Rick's survival with honesty and integrity, and Shane's "dog eat dog" survival. Rick risks himself and his group to perform human and humane deeds. He represents altruism, even though his family is most important to him. Shane, on the other hand, is willing to kill an ally so he can get away from the walkers and bring the needed medical equipment back to the group. So Shane is sort of tribal.

In Jonathan Haidt's very interesting book on moral psychology called The Happiness Hypothesis, he suggests that conservatives tend to be oriented more towards the good of the group they belong to (e.g., family, country), while liberals tend to be concerned with the good of all (i.e., beyond their immediate group). So Rick is kind of a compromise: he does value his family and his survival group, but not to Shane's extreme of doing moral wrong to survive. So this, along with the larger themes of the show as discussed above, makes me think that the Walking Dead is speaking to the new brand of conservatism that is evolving as we speak, that turns away from some of the attitudes of the older generation of conservatives.