The downside of taxing all income for Social Security

From USA Today: Can the rich, famous save Social Security?

...Liberals take an even harder line at denying benefits to the rich, saying the system should be considered a pension program. "It's a breach of faith to make the wealthy pay and get nothing in return," says Michael Ettlinger, director of economic analysis at the liberal Economic Policy Institute.

The idea that rich and poor are treated alike in retirement programs is so central that Kennedy tried to block the Medicare prescription drug benefit in 2003 because it charged the rich more than the poor. "Hold on to your hat," he declared. "Today, Medicare. Tomorrow, Social Security."

Update: Keep the Cap: Why a Tax Increase Will Not Save Social Security (Hat Tip: Social Security Choice)