The network effect changes (very expensive) which limit adoption of proof of work also limit adoption of encryption. Assuming encryption is adopted, the vendor(

The network effect changes (very expensive) which limit adoption of proof of work also limit adoption of encryption. Assuming encryption is adopted, the vendor(s) involved could simultaneously demand using Hashcash or another email proof of work system. One should seriously estimate and discuss the environmental implications of such a change before working towards it though, I think. https://en.wikipedia.org/wiki/Hashcash https://en.wikipedia.org/wiki/Hashcash