> Imagine having to use Facebook to access any money - not just Diems.
I don't think this can happen in practice. For any such system to work at all, the vast majority of the entire society needs to be using it and be satisfied with it, and then there'll always be cash anyway for which there can't be access control enforced by any one entity.
This is something that's been widely advocated. But imagine a private company creating one, particularly one with Facebook's track record.
Imagine having to use Facebook to access any money - not just Diem Dollars.
(my book on Facebook's Libra/Diem plan goes into this, particularly ch 8 on privacy)