Pedophilia, rape, murder, assassination have been going on since Mesopotamia. Communications were always anonymous in the past. You want a 666 control system to try to stop what has always existed and you will get instead your nirvana of megadeath.
Anonymous internet communication doesn't make it more difficult to hunt down individuals as compared to the way it was done before the internet. There was always anonymous money and transactions in the past. Whereas, if we give the State the power to make all transactions trackable in the imminent switch over to digital currency, we will surely all die in megadeath 666.
Two separate issues here. 1) Is there a social cost to adding unbreakable anonymity in monetary transactions? 2) Is the cost worth the benefits?
It is true that such crimes are ancient ones. However, it is also true that the creation of a marketplace where such activities can be financed in absolute anonymity will lead to an increase in said activity.
Ask yourself this question. If everyone in the world was suddenly gifted with your current understanding of fiat, cryptocurrency, socialism and its dangers would you want anonymity in a world currency? The answer in my opinion is no. In such a admittedly very unrealistic scenario there would be no need for anonymity as the populace would vote to dismantle the foundations of fiat based socialism. There would be no justification for facilitating the aberrant social behavior that unbreakable anonymity helps hide.
Now obviously that is a completely unrealistic scenario. However, I believe it demonstrates why the long term solution to this problem is education and where that fails natural selection. Anonymity is a useful means to protect individuals until society progresses to the point where it can be safely set aside.
This problem ultimately boils down to two different issues and a single solution won't work for both.
Anonymity is a shield, not a sword; it will be used to protect innocents and criminals equally in the same capacity. Since there are so many more innocent people potentially in need of protection from oppression/coercion than there are criminals who would use anonymity as an advantage, the societal cost/benefit ratio of anonymity is heavily slanted in favor of the innocent members of society.
Tracking the financial history of every person like some kind of "overseer" may reduce these types of crimes but potentially at the highest cost imaginable. Already, there are genuinely "good" people, very productive members of society who get swept up in the system. For instance, a well liked local high school teacher was imprisoned for several years recently for tax related offenses. When these things happen, society loses almost every time...
Internet anonymity is nothing like burying gold coins. It doesn't have to be cumbersome nor cost more (but there is a lot of programming work that needs to be done to make it so). It doesn't have to decline the velocity of money and can in fact increase the velocity which has been collapsing, by providing an outlet for the private sector to grow and interrupt without the oppression of the State.
Perhaps but this has yet to be proven. Certainly nothing that exists today meets this criteria. The state is likely to come down hard on an anonymous cryptocurrency if it starts to gain traction. That alone will increase the cost of using it.
That's another advantage of anonymity... What exactly would the state "come down hard" on when the state would be unable to determine if the anonymous instrument had been used at all by a specific individual or business? The function of anonymity is to protect the user from the state or any other third party who desires to control or restrict market freedom... They may as well write laws against it, but those laws would be no more enforceable or provable than writing a law against "impure thoughts." The only way to prove that the law had been violated would be by confession or personal record since true anonymity would leave no useful evidence behind...