I think in practice it won't be so much about agreeing on a protocol but rather new apps just parasiting off of the data models of the most popular and successf

I think in practice it won't be so much about agreeing on a protocol but rather new apps just parasiting off of the data models of the most popular and successful apps. The thing about decentralization is that it forces the data to be available. So for example Facebook can't stop an alternative app from having full access to Facebook groups even if they want to. So the big successful apps most likely end up deciding the data model and feature set, and everyone else just borrows that, and if they extend or add features those features won't appear on every interface. Which is okay as long as the common core (determined by the big app) is all there.