There's a proposal floating around in Washington that would "limit the value of the tax break for itemized deductions, including donations to charity, to 28 percent for families making more than $250,000". Foundations in particular have been actively objecting to this proposal. They maintain that the wealthy will give less if they get less of a tax break.
There's a good article in the San Francisco Chronicle presenting the argument that tax deductions are not the primary motivator for donations by the wealthy. And quoting the recent Bank of America study on high net worth individuals, "Overall, high net worth households reported they believe there would be very little change in their giving if there were no tax deductions for donations."
Kind of says it all, doesn't it? Come-on Foundations, you have way more important things to do than lobby against this proposal.