So cash becomes illegal? Cryptocurrency becomes illegal? What do you do if this totally surveilled financial system comes under the control of an abusive state, or the surveillance powers are regularly abused by the state's employees? Have you heard of Snowden's revelations about LOVEINT?

Justice Douglas, in his dissenting opinion on the 1974 California Bankers Association v Shultz case that upheld the constitutionality of the Bank Secrecy Act, provided an excellent argument against warrantless mass-surveillance of monetary transactions:

It is estimated that a minimum of 20 billion checks - and perhaps 30 billion - will have to be photocopied and that the weight of these little pieces of paper will approximate 166 million pounds a year. 6

It would be highly useful to governmental espionage to have like reports from all our bookstores, all our hardware [416 U.S. 21, 85] and retail stores, all our drugstores. These records too might be "useful" in criminal investigations.

One's reading habits furnish telltale clues to those who are bent on bending us to one point of view. What one buys at the hardware and retail stores may furnish clues to potential uses of wires, soap powders, and the like used by criminals. A mandatory recording of all telephone conversations would be better than the recording of checks under the Bank Secrecy Act, if Big Brother is to have his way. The records of checks - now available to the investigators - are highly useful. In a sense a person is defined by the checks he writes. By examining them the agents get to know his doctors, lawyers, creditors, political allies, social connections, religious affiliation, educational interests, the papers and magazines he reads, and so on ad infinitum. These are all tied to one's social security number; and now that we have the data banks, these other items will enrich that storehouse and make it possible for a bureaucrat - by pushing one button - to get in an instant the names of the 190 million Americans who are subversives or potential and likely candidates.

It is, I submit, sheer nonsense to agree with the Secretary that all bank records of every citizen "have a high degree of usefulness in criminal, tax, or regulatory investigations or proceedings." That is unadulterated nonsense unless we are to assume that every citizen is a crook, an assumption I cannot make.

Since the banking transactions of an individual give a fairly accurate account of his religion, ideology, opinions, and interests, a regulation impounding them and making them automatically available to all federal investigative agencies is a sledge-hammer approach to a problem that only a delicate scalpel can manage. Where fundamental personal rights are involved - as is true when as here the [416 U.S. 21, 86] Government gets large access to one's beliefs, ideas, politics, religion, cultural concerns, and the like - the Act should be "narrowly drawn" (Cantwell v. Connecticut, 310 U.S. 296, 307 ) to meet the precise evil. 7 Bank accounts at times harbor criminal plans. But we only rush with the crowd when we vent on our banks and their customers the devastating and leveling requirements of the present Act. I am not yet ready to agree that America is so possessed with evil that we must level all constitutional barriers to give our civil authorities the tools to catch criminals.

Instituting mass surveillance of monetary transactions creates extreme centralizations of power, and the kind of all-powerful government you're advocating creating is a giant magnet for rent-seeking behaviour.