Conventional investing philosophy is that the stock market goes up and down, but over the long run, stocks generally trend upward. This simple principle is what over $10 trillion worth of 401k's, IRA's, pensions and other retirement vehicles are based upon, as well as pretty much every Americans' retirement. Ergo, yes, stocks may be down, but "don't worry, stocks go up in the long run, now might even be the time to buy."
Alas, I think I need to remind people of what happened to the last 1st world nation that suffered from a stock bubble and a housing bubble; Japan.
You see, Japan, back in the late 80's was growing by leaps and bounds, imminently approaching its WWII rival in terms of standards of living and economic power. Because they were destined for greatness, Japanese stocks and property were destined for great price increases. So great that the price outstripped any realistic notion of profitability or rents those stocks and properties could feasibly generate. A bubble formed, then popped and HAS NOT RECOVERED IN THE PAST 20 YEARS;
The moral of the story is that this is a very likely scenario for the US as well and throws a little kink into everybody's retirement plan. Oh, I know Goldman Sachs and American Express and whoever else out there said you can rely on the stock market to provide 10-11% annualized return, but you see it is quite possible many people will never see their 401k's recover, because, well, you can't just live off of increasing asset prices. Profits have to increase as well. And given the utter distaste Americans have with producing wealth (not to mention Obama's insistence on punishing it), a very Japanese like 20 year period of economic malaise and stagnant stock prices is certainly a possibility.
Enjoy working till your 80.