The point of Social Security was to subsidize those who couldn't work, not those who could. The program's founding document said it would support old people who were "dependent," "beyond the productive period" and "without means of self-support." In 1935, that described people around age 65. Today, it more accurately describes people a decade older.
A lot of us think that raising the retirement age (or the age of government dependency) is the right thing to do. But Saletan's piece is the most eloquent that I have seen.
Krugman and Wells note repeatedly that 20 percent of the population is responsible for 80 percent of health-care costs. But that doesn't explain why health insurance should be different from other kinds. The small fraction of people involved in auto accidents in any year is responsible for almost all the cost of auto insurance. You insure against the risk of being in that group.
What's different about health insurance is the opposite: Much of it isn't insurance at all but a subsidy. The value of the subsidy is the difference between what the individual pays and what the insurance would cost in the free market. If people were buying health care or insurance with their own money, they might or might not spend too much—whatever "too much" is—but no one else would need to care if they did.
I recommend reading both columns in their entirety.