The majority of Warren Buffets income is from capital gains, which is currently takes at 15%. Lowering the capital gains tax is why the economy boomed in the 90's. Rasing it is why it tanked under Carter. I would rather see Buffet reinvest his money and buy houses and other goods further helping the economy and employing more people, then hand it over to the govt. Is 15% fair? Consider that he is investing with money that has already been taxed.
p.s. He is all talk anyways, when Bush propsed increasing the tax on private air travel (airspace fees) to cover costs for air traffic since a radar blip is the same whether it is a commercial airliner or private jet, Warren Buffet (Berkshire Hathaway owns NetJets) was against it.