Agree with most that "sheltering in place" decision tree would be hard to override. The "known knowns" of sticking it out would have a distinct advantage over going out to find just about any government response instructions.
It was interesting for me that the FEMA story came out last week while I was attending a "Shared strategies for Homeland Security" conference in Denver, and I was surrounded by CERT, Homeland Security, LEO and other first responders.
http://www.sharedstrategiesblog.com/

While radiological threats did not get top billing, it is easy to see that the whole field of emergency response is changing as we speak, with social media and efforts like wikicrisis changing the face of crisis response.

I opt to stay put at all costs, and until the last possible moment, hoping I can "gather the clan" and "batton down the hatches", and not rely on any government assistance (food, shelter) that hopefully I can provide myself.