Every boom and bust creates its own set of negative and positive externalities which are harder to appreciate at the moment, but its effects only become clear with the passage of time.

The housing bubble during the mid-00s led to a boom in home building, refinancing, renovations, and real estate speculation. The bust led to many people losing their homes, companies going under, and bailouts for the financial system. Now, we also see that the bust led to the underbuilding of homes over the past decade which is contributing to today's soaring rents and homelessness issues in many parts of the country.

We are seeing a major, negative externality emerging with the boom and bust in cryptocurrencies. As the total market cap of the entire cryptocurrency complex soared above $3 trillion, it was accompanied by companies, speculators, and retail traders purchasing expensive computer equipment to "mine" or "validate" these currencies.

Of course, the value and demand for this equipment will fluctuate based on the price of these currencies. Needless to say, their value has collapsed to the point that secondary markets are flooded with equipment that is being severely marked down.

Many of the largest cryptocurrency mining companies are selling their coins and equipment to raise cash to ensure that they can survive a downturn. This adds to the velocity of the downward spiral in both. Further, fewer miners or validators also make these protocols less valuable.

In essence, it's unwinding many of the network effects which drove cryptocurrency prices higher in the first place.

This is an example of negative, real-world externalities as the demand for this equipment drove up prices for many types of chips and contributed to the shortfall in semiconductors which added to inflation and prevented the economy from operating at full capacity.

Contrast this to the dot-com bubble, when there was tremendous investment in fiber optics, IT, and network infrastructure. Most of the companies went bust, but the infrastructure was of lasting value and was essential to the next 2 decades of tech innovation.