Ceding "fact-checking" (i.e. narrative construction) to social media companies (directly, or indirectly by letting them choose contractors to do it for them) is

Ceding "fact-checking" (i.e. narrative construction) to social media companies (directly, or indirectly by letting them choose contractors to do it for them) is a terrible idea. Not only is it unlikely the narrative you receive will track reality in a useful way, but it gives a huge amount of political power to these companies. A much more sane approach, IMO, is to come up with software frameworks where you choose which research firms or individuals (friends, professors, etc.) you want to follow and how much trust you want to assign to each of them. There is plenty of research on ways to do this well in the context of "web-of-trust" cryptosystems.