We can do it incrementally, so that majority op population is not affected much. And if a billionaire is discouraged from earning additional billions and retire - well, that was the point? He stops working (hypothetically) but his place will be immediately replaced by less wealthy successor (or by more wealthy opponent, but that problem need be analyzed separately). His kids won't become billionaires, but will be a mere millionaires, requiring them to contribute if they want to keep up expenses. All in all I think it is possible to set up such inheritance taxes so that majority will have positive result.
If you're thinking about billionaires, I think you're doing it wrong. Billionaires don't have billions in the bank. They generally have shares in companies which need to be sold to get money out. And the price changes the more you sell. Billionaire "net worth"s are almost useless because they assume each share they sell is worth the same as the last share traded, which would not be the case if they were all dumped on the market, and even less so if the government made a habit of seizing your shares when you die.
