Would the outcome be better or worse if we had, say, a 99% tax bracket at >$N million, and let the public decide the best way to deploy that funding via the ballot box? Would that process better align with the values of a democratic society? Or would we just get more corporate welfare, bombers and aircraft carriers?
I'm not ragging on philanthropy--it's awesome that some of these billionaires understand the meaning of "enough" and choose to give away their fortunes to worthy causes. But is it best for society to leave it to a few lucky 'elite' to judge what is and isn't a worthy cause?