Should There Be a 100% Tax Bracket?

Stealing a question from Kerry today, but I think is a good one. Is there an amount of money one can earn in a year for which we as a society say,"O.k., that's enough." Should there be a 100% tax bracket, an amount where once you've made that much, the rest goes to help the greater good? Put it at a hundred million dollars or a billion dollars, wherever. Is there a point where we should say you've made the maximum this year?