P.Steve:

You're looking at the short-term impact of market fluxuations. Something like this a long-term proposition and over the long-term the market returns better than any other option available. Sure, there will be losers in the short-run because of the timing of their entry and exit from investments but over the long-haul the vast majority will be much bigger winners than they get from SS.

Remember that back in FDR's day the prevailing life expectancy was 63 and benefits didn't start until 65...tell you something about the smoke and BS of the time?