[peckrob]

In my case it is predicated on a disaster being localized. Basically it assumes that I will have 48 hours to get a message out.

Where I live is six hours from the coast so hurricanes and tsunamis are not a threat. An earthquake on the New Madrid fault [0] is a possibility although a fairly remote one in any given year. The disaster I optimize for is tornado outbreaks, because it's the most likely to happen. Those occur fairly regularly every few years and are contained enough that I could get a message out probably within 48 hours just by going down the highway an hour or so to get cell coverage.

But to more directly answer your question, pretty much everything depends on power. When the power goes out you have a limited amount of time before backup generators run out of fuel. Even landline telecom systems need power at the switching end. A widespread outage that lasts more than a couple days basically means nothing works and you're reduced to using (like you mentioned) amateur radio or other point-to-point methods that don't rely on ground-based power.

During the Super Outbreak, the cell network stayed "up" for a couple days before going offline completely. But it was impossible to get a message out, most likely because of either demand or damage to the interconnects.

[0] https://en.wikipedia.org/wiki/New_Madrid_Seismic_Zone