Comment by apitman
Maybe I'm being a little too cyberpunk but it would be cool if the system somehow rewarded people for delivering messages over a long physical distance. You could end up with a courier community where runners spend some time walking around high-traffic areas collecting sent messages then jog to the other end of town so the encrypted messages can find their recipients.
At some point, somebody will set up long range wireless communications and then the reward for running a message would likely drop to so small that it wasn't worth it... but yeah that's exactly the sort of thing that I had in mind. That way if something happens to the internet, prices for running a message go up, and suddenly running messages is worth it again.
The tricky part there would be working out a partition tolerant payments system. It's one thing to go offline in the middle of delivering a message, its another thing entirely to orchestrate payment across a smattering of disconnected networks (blockchains are not partition tolerant). I think it could be done, but that's an application layer concern... gotta get the peer finding and web-of-trust stuff working first.