HN user
Yeah you're right. I'm fairly certain also that it's legal for private businesses / individuals to accept and sell other forms of money. Only when it comes to tax payment must you use the State issued currency or suffer repercussions. However we're reminded by Gresham's law that money overvalued by government will tend to drive out money that is not.
Technically, Austrians don't equate "no central banking" with "commodity-based currency". They simply point to the fact that without a Socialist central bank dictating by fiat what currency to use, the free market would simply decide. Austrians point to the historical record that shows precious metals filling this role in the majority of cases where the market was left alone. However Bitcoin seems to be competing now as-well in certain ways which is very exciting.
I suggest you watch http://www.youtube.com/watch?v=TxcjT8T3EGU on trade cycles before the Fed.
I find the argument that Gold and Silver are currently in "bubbles" to be unfounded. I think in the future as central banks across the planet continue their reckless expansionary monetary policies, the potential is certainly there. However I don't think we're at that point yet. If you contrast the current precious metals market with the tech and housing bubbles, you don't see the masses running out to buy gold and silver on credit. Nor do you have a Federal government subsidizing this behavior adding more air in the bubble.
Mr Tucker is truly a treasure. If anyone is not familiar with him or the ideas, check out mises.org