I see a few smaller funds collapsing due to a bad year of returns. Those funds will put pressure on the PBGC which will in turn raise rates on other pensions which are underfunded. That will cause more funds to collapse (and the market will get more unstable as investors either are withdrawing more to make up for lost pensions, or are trying to figure out the winners and losers inthe pension collapse. At this point, Illinois or Calpers will have signs of collapse, and the tax burdens of California and Illinois will increase dramatically. This will lead to more flight from taxes, causing the Feds to step in. This is when the effect on the entire population will be most likely. Fed taxes will rise, "entitlements" will increase, inflation will rear its very ugly head, and the 30's will return. The only way out of it is a major global war to ramp up the economic war engine, and reduce the population. At this point the best currency you could have will be food and ammo! (just kidding).
How will this affect me? I have no pension, so the collapse of the markets is when I will be hit, and I have 3 sons who are in their 20s who would likely be cannon fodder in any war.