I've posted this before, but it's good to keep this in mind when listening to Obama casually assume that there is no problem having the rich pay half again as much as they are already paying (see my post on Obama's math from earlier today). This chart shows the cumulative share of taxes paid by top income earners, according to data from 2006 (e.g., the top 1% pay 40% of all income taxes, and the top 10% of earners pay 70% of all income taxes). To be in the top 1% of taxpayers you've got to have adjusted gross income of just under $400,000. Obama defines "rich" as those making at least $250,000, and that would consist of roughly the top 2% of income earners.
As a rule of thumb, the top 2% of taxpayers are probably paying close to 50% of all income taxes, which in 2006 totaled a bit over $1 trillion. Federal revenues for calendar year 2008 were $2.4 trillion, just about exactly the same as they were in 2006, so it's safe to assume that total income taxes haven't changed much since 2006. (Corporate taxes are a little over $300 billion, and payroll taxes are about $650 billion.)
It's hard to keep track of all the new spending Obama is proposing, but between the stimulus bill, universal healthcare and bank bailouts—plus his call for a general increase in the federal budget of 8.5% for the next year—it could easily add up to an extra $300 billion a year for many years to come. Do the math: the "rich" are currently paying about $500 billion per year in income taxes, and he presumably wants them to pay an additional $300 billion—a 60% increase in their tax burden. That is just about impossible in my book. Something has got to give.