>There's not some program you can "donate" bandwidth to and make money off of it.

There is one:

https://pkt.cash/

from the maker of https://github.com/cjdelisle/cjdns

And there is https://sia.tech/ (Network too but mostly about storage)

Are there any hosting companies not named Amazon or Google? I could see how for a small-scale operation it could be beneficial to host a redundant server for backups... but even then, I am not sure how much that is really worth.

DigitalOcean and Backspace are still doing brisk business, and very competitive for some segments (Gameservers and the like)

Also check out Linode and Hetzner.

^ Vultr also exists

If it's just backups there are tons of options out there. Backblaze for example.

The security implications of running your own AWS cloud infrastructure with API building blocks for people to use to build their own infra sounds like too much for a one man shop.

Isn't one (or more?) of the alt cryptocurrencies about distributed bandwidth sharing? I recall something using that combo of buzzwords from 2018 or so, but I can't think of specifics.

"PacketCrypt is a bandwidth hard proof of work, this means it requires lots of bandwidth to mine. Miners collaborate with one another by sending small messages (called Announcements) and the sending of these messages requires a large amount of bandwidth." https://docs.pkt.cash/en/latest/mining/ https://pkt.cash/