And now the history repeats itself: - In the same way that apple- and potato-certificates could have different values, how do you know which IOUs you can trust

And now the history repeats itself: - In the same way that apple- and potato-certificates could have different values, how do you know which IOUs you can trust? - Someone says: "Hey, instead of giving IOUs to each other, come to me. I'll figure out if the person is actually able to pay it back later and give him money." Instead of having the IOU accepted by everyone in the village (a seller won't accept an IOU unless he knows he can trade it with other people, so a buyer needs to prove his credit to everyone), there's only one person/system who needs to accept it.