[hjnilsson]

Such a tax would have a lower bound on wealth (that is how it works in all countries with wealth tax). Only wealth above a set limit (say 1 million dollars) would be taxed. It would not affect people's incentive to save. In fact, if it makes wealthy people spend more of their money, that could conceivably be a net positive on the economy as well (less stagnant money).

[lagadu]

That would just lead to (further) portfolio diversification, where you buy assets abroad purely as a means to store value instead of keeping all your assets under a single country's control.