Being decentralized and anonymous, the first task of course is to figure out how exactly to tax it.
morons love the state.
they will tell them.
Please keep separate what is currency and what is taxation. Whether you can tax gold or not is irrelevant to gold as a natural substance. Same with bitcoins. Taxation is a social construct which applies to transactions, income, gains and assets.
If you own a property the government may tax you 1% of its value per year. It is irrelevant whether the prevailing currency the government uses is dollars, euros, gold, bitcoins or sea-shells.