Let's say I am an owner of gold and a seller of gold certificates. People would like to use gold, but it's hard to buy and sell things with it. I am honest; and trusted (people already buy my certificates).
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This would be utterly pointless.
If people have to rely on a central counterparty to redeem their certificates for gold (or anything else - people have proposed that share registries might be maintained in a bitcoin block chain but again that would be pointless) that central counterparty might as well maintain the database of who owns what. There's no benefit to having a complicated distributed database like bitcoin for that when all the risk is already concentrated in a central counterparty. If your central counterparty is going got cheat you then they will. If the government forces the central counterparty to take some action then they will. It doesn't make a damn bit of difference if the central counterparty keeps the records of who owns what in a simple spreadsheet.