When reading this thread the following comes to mind...
Double Spending
Double Spending is an understatement.
Some sources suggest that said gold holdings have in fact been sold
and re-issued as bonds and gold certificates to banks, companies and citizens. These bonds and gold certificates have then been re-packaged and re-sold multiple times in the markets on top of assets that don't actually exist.
[Citation needed]
So... Triple and even Quadruple spending of 'borrowed' assets.
Google rehypothecation. In the City, rehypothecation can be infinite (but limited, by haircuts).