I wonder if Delegated Authentication can be enabled for a specific set of users in addition to Social Sign on. The idea is that a specific set of users can login to Salesforce either by providing username/password (which is going to be validated via Delegated Authentication) or by using their Facebook credentials.

All the examples that I saw so far were showing that Delegated authentication and Social sign-on can be enabled in Salesforce. My question is if they can be enabled together for the same set of users.

Federal authentication is not an option for multiple reasons.

Thanks