> “The danger is the creation of an electronic black market, similar to the cash economy,”
But how can they avoid it if Bitcoin does work like cash in many aspects and they have no control over it?
It will be (almost entirely) up to trust in the long run.
The NSA knows the physical location, email address and browsing history of nearly all US based bitcoin addresses.
It was only within the past decade and a half that the IRS even acquired the ability to to spot discrepancies in returns based on filings from different taxpayers (due to the increase in e-filed return. Before that, enforcement relied almost entirely on random audits and tip-based investigations.
At some point you spend the money, and the difference in spending and taxes paid gets their attention.
To avoid scrutiny, you'd have to either not spend the bitcoin at all, or only buy inconspicuous things with it, perhaps intangible things like streaming-video subscriptions and videogames.
How is that not enough control?
If you buy a burger with bitcoin, then, well, noone cares if you didn't pay taxes on that; but if you buy a car or a mansion with bitcoin (or bitcoin-derived resources), then the item is visible, and they can audit your income and purchases to trace the source of that money (and untraceable source = your problem).