One unintended consequence is a reduction of competition, medium sized construction company sells out to bigger construction company either before or after the death of the owners. I have watched this in the highway construction business, and I imagine states are overpaying for work in less competitive markets.

The primary purpose of the estate tax is to serve as a welfare system for lawyers and life insurance companies (both lobbyist-rich of course). A secondary purpose is to feed the envy of the left.

If the administrative and enforcement resources were shifted to tax evasion we would collect more money.