I asked an administration official to respond to the question about whether charitable contributions will decline if itemized deductions are reduced for those making more than $250,000: 

"Right now, if a middle class family donates a dollar to their favorite charity, they get a 15-cent deduction, but Warren Buffet and Bill Gates make the same donation and they get a deduction that is more than twice that.  The proposal walks that back some of the way because it's time that everyone is responsible for our future."