I agree with you in general. A few observations: Radio broadcast does scale "infinitely" in terms of the number of possible "clients" connected to the "server"

I agree with you in general. A few observations: Radio broadcast does scale "infinitely" in terms of the number of possible "clients" connected to the "server". It has no limits to the number of possible "connections" - because, of course, it's actually connectionless. It does suffer from severe bandwidth limitations. For emergency communications this is not a problem. FM (or anything above 30 MHz) also has very limited range - line of sight more or less. Frequencies below 30 MHz could and do occasionally reach the antipodes. Also keep in mind there's a network of radio operators that is everywhere, and we are prepared to intervene in case of massive telecom collapse - the HAM radio operators. Emergency messaging should continue to function, at least for a while, even in the context of massive catastrophes.