This post is not about how the United States Federal Reserve cannot control, on a day-to-day basis, the quantity of money in circulation. Rather, I consider financial innovation over time leads to the creation of new debt instruments that fall under a reasonable definition of "money".
One way of looking at money is that, under capitalism, money buys goods, and goods sell for money, but goods do not buy goods. A simple example: I understand one can write checks against a hedge fund. So hedge funds are money.
The emergence of new forms of money illustrates why no final systems of regulations can exist in a capitalist economy. Should something like the Federal Deposit Insurance Corporation be set up to guarantee these new forms of money? If so, some capital requirements, restrictions on leverage ratios, and so on would need to be instituted. Maybe some sort of firewalls, as in the Glass-Steagall act, should be rebuilt.