The problem with defined benefit is there are always unknown risks. You can say that the government, or an insurance company will pick up the tab, but what if

The problem with defined benefit is there are always unknown risks. You can say that the government, or an insurance company will pick up the tab, but what if they fail? If the amount of the benefit is large enough (retirement savings for a generation) it's impossible to guarantee. Small #s yes, large, no. Many intelligent people don't believe a small system like Social Security will hold.