<Seems to me like the inheritance tax has double benefits, on the one hand reigning in the abuse of power acquired through wealth, on the other encouraging the use of wealth in ways that benefit society (and I can't stress too much, in the judgment of the philanthropist).

This entire statement, and the inheritance tax, is based on the premise that if the wealthy are allowed to keep their money, they will do something stupid with it, whereas if the government gets it, it will do something brilliantly useful with it. I'm sorry, how's that again?

Don't see you worrying about the government using the wealth to get too powerful...