If you only tax "> $X" then you aren't really stopping anyone from reaching $X.

I guess you can argue that they're WAY above $X and this is a way to prevent people who reach $X from climbing, but let's be honest the system is mostly rigged that way as it is.

The most impact I see would be on people for whom non-liquid assets comprise the majority or entirety of net worth. Take a YC unicorn for example. As soon as a 409a valuation puts the value of a founder's common stock above $50m (in Warren's plan), the company has to start thinking about a liquidity plan in order to support the payment of wealth taxes. Unintended consequences could be further concentration of ownership and upside in VC/PE hands, more pressure to IPO sooner, or decreased appetite for risk among founders once they've hit a certain threshold.

Pressure to IPO sooner would probably be a good thing for most people. Index fund holders got to benefit from the rise of Amazon and Google much more so than the rise of Uber. Public company accountability mechanisms may put a damper on some of the founder -led vision that private cos are willing to abide, but generally it would be better if the wealth were spread around.

There may be unintended consequences in the current scheme that we've just grown to accept too (like an always increasing wealth gap).

If you only tax income then you definitely impede people reaching certain levels of wealth.