To me, the #1 marker of "crazy" in disaster preparation is a focus on violence against your fellow civilians, and I'm glad that this guide pushes that out into the far end of unlikely and extreme end of scenarios.
From reading forums the other marker seems to be those 'who know' what they are prepping for e.g a solar flair or nuclear bomb is going to happen. This vs. the attitude disasters can happen and to have general coverage.
And if you look at the history of the world it's reasonable to have some level of prep going. Disasters are low chance but consequences are severe. It's reasonable odds at one point in your life there will be a major disaster. Historically it's unlikely to get through 2 lifetimes without something significant happening. Most people have house/car insurance for these low risk events but feel prepping is unusual. I'd prefer to have some coverage from a low chance but high consequences disaster than have the cost of replacing a car covered.
For what this scenario actually looks like, a post on Metafilter about Sarajevo: http://www.metafilter.com/78669/What-if-things-just-keep-get...