You don't really need to. In IOU systems you extend credit to someone you know, based on ones reputation or credit score. How back in the day your local milk man would just keep a tab of what you owe.
In a way everyone has something to barter: you owe the milk man, your employer owes you. Identities form a web of trust in the physical world.
In a way everyone has something to barter: you owe the milk man, your employer owes you. Identities form a web of trust in the physical world.