The wild thing is that the stock market is inextricably linked to the health of the economy, with employment and inflation flagging one another with every move the stock market makes. In 2008 we saw some wild collapses in both the stock market and real estate, and shortly after that the layoffs began. We honestly *need* the stock market to correct at present to preserve what has largely been a "normal" economic ebb and flow. If it continues just going through the roof unabated the fall is going to be cataclysmic.
Discussion
Well, in general a healthy free market will have companies that have losses or fail; as Thomas so well said 'losses are just as important as gains', losses are a signal to correct the misallocation of scarce resources.
The problem today is, we passed the rubicon of the threat of cataclysmic downside a long time ago; our fiat system is based on the issuance of debt, every dollar in circulation was created as part of a loan (home loans, government bonds etc.) with a corresponding interest rate; to keep the dollars flowing, we have to issue more debt, making the problem worse for the future. If too many businesses fail and can't repay their debt, the banks can't make repayments on their debt and fail, now people can't withdraw their money for paying their home and auto loans and those lenders get screwed, its contagion. Is this a risk today? Well, there's maybe $1-1.5 in circulation, there's ~$32T in government debt, $5T in credit card debt (I think that's right), ~$170T in unfunded liabilities, and $2,000T in derivative exposures for top level bankers like Goldman Sachs and JP Morgan. So, yes, its a debt bomb, its designed to cause so much economic upheaval that it scares the public into bailouts like we had in 2008, and so the cycle continues.