Comment: currency is just

a way of transmitting information. The value of anything arises out of the transaction, and has nothing to do with the material.

If everyone refused to accept transactions with gold, then gold would not be money.

The utility of gold as currency comes from the difficulty in manipulating the value over time. I don't know enough about how bitcoin works to say how hard or easy it would be for some group to manipulate its value to their advantage, but, if it is as difficult as silver and gold, then it is as good a currency. It is clearly a much more convenient currency.