Room For Debate addresses the question. I'm with Veronique:
Americans over the age of 65 are in remarkably good shape compared to those of previous generations. Their average net worth has increased almost 80 percent over the past 20 years; they form a larger share of the high-income group and a smaller share in lower-income group than their predecessors; they are far better educated, and they live longer and healthier lives.
...The best option is to cut benefits. One way to do that is to raise the age of eligibility to at least 70 and then progressively increase it to track with life expectancy. This won’t be popular, but Americans’ dependency on government programs is less entrenched than that of Europeans.