Bunkers?

I am more than a little curious with the level of hysteria that seems to be bubbling right under the surface. Rumors of ammunition shortages from people stocking up. People stating over and over in various conversations "we just don't know what is going to happen". While searching for the Feingold approved dino nuggets on the Costco website, I come across a whole selection of shelf stable, prepackaged foods. A 6 month, 4 person supply for 2 grand and people are buying this?

Is it normal human nature to assume the worst will happen? Are we entering another 'cold war era' where everyone builds underground bunkers and stocks it with supplies? Am I missing something by not buying into all of it?