I beg to disagree that the nature or essence of currency is consensus, at least not until Bitcoin came. It may be so in a small and primitive community but it cannot be in an advanced and large society.
The fiat currency is made up of a lot of policies, decisions, changes, impositions, etc which are not out of consensus. Of course it could be argued that it is hard to gather the opinions and ideas of everybody and that the very reason why there is a government is that it would act and decide on behalf of the larger population.
However, this is not really the case about fiat. The decisions of the few persons who decide about the direction of the currency are not really reflective of the people's voices and sentiment. So everything is merely imposed on the citizenry whether they like or not.
As far as I know, money in the state (cash and non-cash) should be issued as much as there are material values in civil circulation that can be commodities. There is no room for any consensus here, this is pure economics.
It is still difficult for me to say how bitcoins and other crypto-currencies will flow here. States are unlikely to take them into account in general economic processes, but the capitalization of the cryptocurrency is growing and something will need to be done about it.