True, that is a very simple decision that probably would be enough for preventing current cryptocoins for increasing his market cap beyond gold. Cryptocoins created by governments would be much more convenient as they would have less strict anti-laundering and tax regulations.

On the other hand, biggest central banks are limiting cash operations, and they may completely ban cash when their cryptocoins are mature enough. Then the black money will migrate to monero and similar cryptocoins. My question is: the future crypto black market will be bigger or smaller than current cash black market? I hope it would be smaller, but I am afraid it would be bigger.