Evil Monkey, I quite agree with your thoughts on what the zombies, particularly in the closing shot, were representative of metaphorically. Very nicely put.
I wasn't expecting such a bleak ending but I sure did like it. I also liked how the intelligence factor on the characters seemed all swapped around after the zombies hit. Before the outbreak most of the Big Brother contestants seemed kind of idiotic but quite a few of them really kept their heads when everything hit the proverbial fan. Unfortunately it wasn't enough for them, but still a nice change from your average horror fare.