I'm thinking of it by analogy to the way that btc depends on energy scarcity. A PoW token is in some sense an abstraction of energy, like a joule wrapped up in computer code. This mapping between something finite (because of the physics) made abstract (because of code) is the magic transformation that allows btc (or dna for that matter!) to collapse the infinite space of abstract reality into something that behaves as if it were finite and concrete. Physics comes with a very handy, fungible source of scarcity (energy) that we can use, abstractly, as money (or food!) but extending "consensus about account balances" to "consensus about interesting content" involves moving to a higher dimensional space. At this point it makes sense to ask the question of what should we model as being scarce in the social realm? Reputation is the obvious answer, which is why most client's have defaulted to whitelisting a set of well known people as the root source of scarcity from which consensus flows. But that's not a granular or self-regulating solution. I don't have a fully formed answer yet but intuitively I think there will end up being something akin to miners which validate the formation of social capital.