isn't that the job OF a middle man to ensure security?
It's your job now. It's up to you to decide who you can trust, and to only send money to trusted people.
i mean, isn't this the very basis of government, as this 'public' third party figure, because people ultimately are unable to trust each other.
That begs the question, if people are unable to trust each other, how can they trust a third party? (Especially if that third party is someone they've never met, never talked to, never voted for, and enforces arbitrary rules on transactions while taking an exorbitant fee for their "services" which in many cases are neither requested or desired.)