I’m fairly sure I’ve seen an NNTP based imageboard that distributed it’s content through that protocol and different instances had overlap of boards. That’s about the closest match to federated system you’re going to find with this model I think. Interesting concept. Not something I’d want to interact with personally though.

Slight difference is that Zuck has had control from the start, whereas other companies might have had “don’t be evil” leadership that was… optimized away for financial reasons.

Not that it really matters nowadays. Just an observation.

Re profiling, I don’t think instances will bother doing that (unless they start running ads). However, they also don’t prevent anyone from building that profile themselves from observable behavior. And creating such database might constitute original work by itself. Now, they don’t get as fine-grained interactions as you would with tracking-infested sites. But they will get the most valuable ones such as active participation.

I’m probably missing something, but wouldn’t it be far easier to redirect people to install page of extension for their respective browser? Such extension could then transform the button as needed to point to whichever social web instance.