a very common early form of money was butter. Its hard to produce, easily divisible, compact in relation to value, and likely to be valued by others.
Early money sprung up out of a need for a common medium of exchange, and was backed by nothing except the belief that others would accept it in payment for their goods and services.
Rand seems to hold the common belief that certain materials are imbued with intrinsic value. I disagree. Value is created in the minds of men, and is the product of our wants, needs, and desires.
In my opinion bitcoin has the same level of counterparty risk as a gold coin. It is as silly to say that it should be backed by stocks, as it is to say that a gold coin should be backed by stocks.