So, Mordor was actually a lovely.

As to Facebook's own cryptocurrency, it would be centralized. Otherwise it wouldn't be a Facebook cryptocurrency, would it. It might be a bit wasteful to set up a blockchain to maintain a ledger of monetary transactions for a centralized organization unless they were planning to share it with other organizations eventually. Who knows, maybe Facebook will implement a fiat payment system of one kind of another. It would facilitate commerce on Facebook which is a non-negligible use case for it.