There’s nothing innovative about issuing IOUs.

Bitcoin, and multisig specifically, made federated custody of base money possible, that's a monumental breakthrough in 2012 or so. Eric discovered an obscure cryptography paper that made federated blind signatures possible, that's fedimint 2021 or so. Combine both, and you have a federated money warehouse with federated custody and federated anonymous IOU accounting. Money warehouses have always been, and will continue to be, an ethical and useful service that entrepreneurs provide. These two tech breakthroughs just take it to the next level in terms of security and trust assumptions.