[rphlx]

That may be the protocol at launch but the protocol can always be changed/hardforked, including (as an extreme example) to just centralize the system into VISA/MC style db at FB after achieving wide adoption.

AFAICT power ultimately rests with whoever can modify the most widely-used consumer SW implementation, which would probably be FB here. Though Apple and Google may have considerable veto power over updates pushed through their app stores, iff FB makes this primarily a cell phone app instead of a web app.