Dominance is defined as being the recommended industry standard or de facto standard---a majority of users.

If ambiguous (e.g., no clear dominant protocol due to difficulty counting true users), this will resolve to N/A.

Even if a centralized platform is still dominant (e.g., Facebook, Twitter), this will resolve to the most widely used decentralized protocol/industry standard.

Protocol: A system of rules that allows two or more entities of a communications system to transmit information

A social media protocol needs to:
1. support sharing of content by users;
2. support interaction with the content of other users;
3. have permanence/persistency.

Counterexamples:
RSS---no interaction.
IRC and Matrix---not designed for async access with persistence.