As I’ve said before, if we’re going to cut spending on retirement programs then it makes much more sense to reduce Medicare outlays by $1 than to reduce Social Security benefits by $1. Social Security benefits can be used to buy health care, and reducing Medicare spending could reduce system-wide health care costs. What’s more, if we’re going to cut spending on retirement programs then such cuts should be broadly shared and not exclusively inflicted on younger people. Such moves are both fairer and more credible. Last, if you want to cut Social Security benefits you should just cut Social Security benefits. Reducing outlays via the mechanism of a higher retirement age is going to mean that the incidence of the cuts falls most heavily on people with physically taxing–or simply boring and annoying–jobs. It’s one of the most regressive possible ways of trimming spending.
That's from Matt Yglesias.