This data is from 2007 and the top 1% paid 40.4% of all income taxes compared to 39.4% for (almost) everybody else. Since then, Obama has proposed allowing the Bush tax cuts to expire, an additional surtax to pay for government-run healthcare, raising the cap on Social Security taxes, and a limit on deductions for charity and "Cadillac" private health care insurance.
But let's put money aside for the moment: what does it mean for our democracy when a very small percentage of Americans pay all the taxes? Inexorably, it leads to a plurality who will always support a larger government because somebody else is picking up the bill. Eventually, to evoke Margaret Thatcher, the government is going to run out of "other people's money."