But how would you make as much money as FB does off a very useful tool?
Possibly a mastodon based solution where users pay a small recurring fee for server management and some R&D and offering privacy, could generate enough benefits for a company (or companies) to strive.
FB (among others) made us forget the sense of scale and the value of things, including the value of privacy and brain time. I would rather pay today from 1 to 5 USD a month for a service that works, where I can share my kid's pictures with my direct family and only them, with no ads.
There is also a difference with what it actually costs to provide the useful part of the service. Mastodon is open source, yes it requires hardware (virtual or actual) and operation, none of which is free, but the cost of these certainly doesn't match the cost of running+developing game changing (advertisment/recommendation) ML models and ultra high scale infrastructure. Running a mastodon server for a thousand users with acceptable availability, and no fancy ML or R&D, I think should be doable for $5.000 a month, yes.
* use the great social graph that you now have to create other useful tools that you can monetize