Disclaimer: I don't really have a horse in this race, and I think most NTFs as currently bought and sold are scams. But I do strongly disagree with much of this article, and I think the underlying technology is pretty sound.

> An attacker with 51% power could invalidate all new transactions for other users, and could for example slowly start limiting the transactions of other users or companies using the currency (targeted or otherwise) unless they paid a certain amount to the 51% owner. Once a currency is embedded enough in the economy, it will not be a feasible option for people to simply abandon their money and start over (and you won’t be able to sell it in such a situation). Like all such situations, an attacker would use a form of salami tactics, slowly taking a bigger and bigger cut from other people’s money via transactions whilst doing it slowly enough to stop them from moving away from the platform. Even in the event that the cryptocurrency later dies, the attacker will easily end up with more real-world currency than they started with.

The idea of a single entity holding 51% of all of a circulating currency is completely at odds with the notion of a currency being "embedded enough in the economy" that people won't just dump the currency immediately and crash its exchange rate. Even the richest individuals alive have nowhere near 5%, never mind 51% of all circulating dollars.

The section on Byzantine fault tolerance is particularly baffling.

> Consider the aeroplane again. What motive does the sensor have to malfunction? None. As a result, we can be relatively sure that its failure would be down to one of three main causes:

> Software failure

> Hardware failure

> Human inteference (e.g. a soldier tampering with sensors on an enemy warplane)

> Byzantine fault tolerance is excellent at protecting against the first two possibilities in many systems. It is much weaker against the last possibility, because the human who sabotages the plane has a motive for the sensors to fail in a specific way which will breach the maximum fault tolerance of the system. Provided the human or humans can tamper with enough of the system, the fault tolerance breaks.

This is the exact opposite of how Byzantine fault tolerance is defined. The entire point of Byzantine fault tolerance is that some of your nodes may not just be faulty, but actively adversarial. In the original Byzantine generals problem, some of the generals are active traitors.

These issues made it hard for me to take the rest of the article seriously, but the author does raise good points with regard to how users are generally the weakest link in a given security model. If someone tricks you into sharing your Bitcoin credentials with them and steals everything from your wallet, good luck getting any kind of regulatory authority to recover your money. This is one of the main issues of cryptocurrencies when compared to centralized currencies - but that assumes you want to trust the central regulatory authority to begin with.

Personally, while I think NFTs as a concept are fairly useless as currently applied (buying and selling URIs of random images that you may or may not actually own), they're not an inherently bad idea. For example, shares of stock in a virtual company could be minted as tradeable tokens, and then dividends could be paid out periodically to whichever accounts currently own tokens. In this case the entire concept of ownership is embedded into the token itself, so you don't need to rely on any external resources.