Money which is hidden from balance sheets and audits can still exist as long as there's some way to convert it into real goods.
The awful toxic horror of money is that somehow these debts become illusory assets which exist for exactly as long as people believe in them.
When that confidence disappears, so does the value.
The only way to avoid a manic depressive economy is to ground value units in items with real physical value - not gold or silver, because their value is mostly still symbolic, but in the products of the ecosystem and in energy flows.
It's impossible to have a viable, stable economy when no one knows how much units of exchange are really worth, or when currency is subject to insane cycles of emotional and psychological excess.
And the real problem is that they may then be accepted as collateral for loans.
This is like what happened with subprime. A NINJA-mortgage salesman comes to an unemployed black man sitting in a porch in rural Alabama and asks him "would you like to own this house before it falls over?" and the man says "sure" so he gets a mortgage he will almost certainly end up defaulting on. But now he's a homeowner! So next time he goes to the bank they ask him "are you a homeowner?" and he ways "yes" and they offer him "how would you like to have a credit card?", so he gets a credit card. And so on. Most economists teach a theoretical framework that has been shown to be fundamentally useless. -- James K. Galbraith