How in the world did his secretary pay 30% in taxes? Even if she's single with no kids, her total income tax would be significantly less than that. (Her marginal rate might be 30%, but that wouldn't count deductions and exemptions.) The only way you could get it up to 30% would be if you included other taxes -- FICA, Medicare, real estate, sales taxes, and so forth -- but Buffett had to pay those himself, and was surely not including them in his 17.7% rate. True, he doesn't pay FICA for income over some small amount ($80,000?), but that is because we maintain the fiction that FICA is a sort of savings account, and we don't give benefits for earnings over that amount. (Not that I agree that it works that way, but that is the justification for it -- if someone wants to argue for a reduction of the FICA tax, I'll be all for it.)
One might also point out that the government could tax Warren Buffett at a 90% rate and he would still be fabulously wealthy. That's not true for people making $250,000, which seems to be the magical point when one becomes classified as rich these days. How about a higher tax rate for people making over $1 billion per year? I'm not necessarily in favour of it, but at least they would be in a position to afford it.