The use case that I think is: A competitive marketplace to compete for the best use of encrypted data. Where each data point and evaluation has a 'cost' to the system and each algorithm competes and entirely based on pseudonyms. Since how we perceive 'trust' is etherial/intangible/ever-changing.
I don't think the solution is an easy one to create but I do think the building blocks to them are (no pun intended).
It's not simply just a ledger.
I'm talking about every data point that facebook has, to be hashed and competitively manipulated in a global market place.
Trust is very relative but using a bitcoin-like solution would allow for the market to compete for the better solution, each and every day. Facebook's authoritarian solution won't last forever, nor should it; allowing competition through FB's data could be a way that FB stays in the limelight.
Anyway I can't understand what the use case would even be here. You need FB to publish their rankings publicly which doesn't need to be decentralized, or you want each person to have their own rankings which don't need to be distributed?