Here, Tabarrok outlines a couple of views on Social Security.
Person 1: Anyone who thinks SS is a Ponzi scheme is nuts.
Person 2: SS is a Ponzi scheme that WORKS! A growing nation is the greatest Ponzi scheme ever contrived.
Person 3: SS is a Ponzi scheme...may or may not work. Tabarrok doesn't specify this person's view.
Person 4: SS is a Ponzi scheme that used to work great, now it has just gone flat and may even pay you less than you put in.
Persons 2, 3, and 4 are all Nobel Prize winners.
Oh, a Ponzi scheme is an investment scheme where people who invest initially are paid returns from money invested by other people (or their own money) not from any returns actually made through investing (think Bernie Madoff or Tom Petters (this guy dated my cousin!!)
So, is SS a Ponzi scheme? For more info, read the links!