Flannery O'Connor's got nothing...
Believe it or not (and many may not...the same way many don't get Flannery O'Connor), at the heart of this movie is a very Catholic interpretation of what a Christ-less society (as opposed to one preparing for Him or following Him) is by its nature - both in its good aspects and in its bad, and the reality that mere civilization cannot save itself, because it is nothing itself but a gathering together of families, who are composed of persons, each of whom need someone else to save them. This movie is about the "hole" that we each have in our hearts that the world cannot fill - only salvation can. Grace.
The movie itself rests on the premise that it is the "family" that lies at the center of everything human - relationship is what we are made for, it is what drives us; and it is family that is at the heart of a society. A society that attacks the family will destroy itself on the altars of pagan gods, and all of them demand beating hearts, whether it is the sun god or the CEO job. Of course, the movie also manages to veil our view of this premise through much of the time by the use of said beating hearts... But then again, doesn't our culture do the same thing?
I'd go on pondering, but it's late *ahem*, and I don't want to give too much away! There are some amazing messages in this movie for our culture - but I doubt many people will get past the gore to really see them. I guess that's why we need priests to be good homilists!! :)
Let me think about this film some more... like when I'm awake. There's much more to be considered here.