Exactly -- or with a piece of their real estate! Just take a chainsaw, cut a bedroom and bathroom out, and the government gets that piece.

In the proposal, people whose assets are mostly illiquid are excluded from this tax.

Ignoring the many other reasons why that would be problematic, what happens when the US government suddenly owns notable (or even controlling) stakes in companies?

You would effectively have corruption. Governments would be more reluctant to take actions which could be negative when they have direct ownership vs their normal "indirect ownership" via taxation.

> what happens when the US government suddenly owns notable (or even controlling) stakes in companies?

This is effectively similar to nationalization, along with the pros and cons that come with it.

I'd love to see a list of pros. There are no pros. It's effectively death to competitors and actually extremely damaging to the companies themselves as well.

Make those shares non-voting,

Or tax them on the loans they take against their assets (effectively realized gains)... problem solved without tanking the economy.