Bitcoin has never really been currency anyway; it's more of a pseudo-futures contract than anything else. IMO an essential criteria for a currency is that it is backed by an economy and a government with the power to ensure the security of that currency.
Prostitutes are expected to pay tax on money they earn. Drug dealers are expected to pay tax on money they earn.
Paying tax is nothing to do with legitimacy.
I.e. Drugs and prostitution should not be illegal.
IOW...you are taxed on your gross criminal income.
Maybe that's better in the U.S. then..
[1] http://www.nu.nl/algemeen/472183/crimineel-kan-pistool-decla...
It doesn't matter what some people think about drugs - The Government spends vast amounts keeping them illegal and criminalising people who produce, distribute, or consume drugs.
Almost all of The Government sees no legitimacy in drugs.
The IRS will see drug money as taxable money.
The fact that tax authorities are happy to accept tax from illegal revenue means absolutely nothing about the legitimacy or otherwise of those activities.