According to- Melissa Lin: Increased risk of security breach: A cashless society may bring about increased risks to personal and national security. From a personal security standpoint, the risks we already experience when we lose credit cards or our phones would only be exacerbated in an environment without paper currency.

Cash is one of the last man-made means of protection that he or she has against governments that have grown to a degree of power that they never had before.

The Dangers of a Cashless Society
There are two predominant dangers that come with a cashless society, and just about every negative that you can think of due to such will fall into one of these two groups:

Denial of purchasing power
A complete loss of anonymity
Denial of Purchasing Power
The Threat Of Cashless Societies
A cashless society is a controlled society. If everything must go through an online banking or credit card process, then you have just lost virtually all control over what you buy.

Anything that is not politically sanctioned(guns, ammo, body armor, helmets, particular books, particular website premium subscriptions, political donations, etc.) could very easily be vaporized overnight.

This, of course, would drive the makers and holders of such products into a black market to barter their goods, and this in turn would be responded to by the use of overwhelming government force. This will come in the form of Stryker vehicles, concussion grenades, snipers, and men with automatic rifles and body armor.

Don’t believe me? Read FA Hayek’s The Road to Serfdom. Totalitarian governments must resort to force simply for the sole reason that people will naturally refuse to comply with widespread theft of their own goods. This force will only continue to grow in its usage.

Totalitarians do not accept blame for their own economical failures. The state is the end of all things to them, and as such, the end justifies the means – no matter how terrifying such a means may be.

A Complete Loss of Anonymity
Once cash is abolished everywhere, your attempts at any form of anonymity will be destroyed.

The Threat Of Cashless Societies
You already have an amazing amount of data that has been collected from you from your Internet search history, GPS data, voting history, bank statements, credit card statements, phone data, and a host of other publicly available information that easily allows people to deduce information from you.

And where humans fail, algorithms thrive. I have a hobby interest in algorithm creation (particularly multiple linear regression analysis) and have used it within my healthcare job as a means of predicting patient attendance rather accurately on any given day. I’ve also used them to (somewhat less accurately) predict when a patient was going to have episodes of heart block.