However, there is no shortage experts who are waving red flags. Earnings expectations have been falling, profit margins appear to be unsustainably high, and sentiment is so high that it seems investors are being complacent about the risks.

"Every reliable technical tool is warning of major peaking action," said Walter Zimmerman, the senior technical analyst at United-ICAP. "This includes sentiment, momentum, classical chart patterns, and Elliott wave analysis.

"Most of the rally in the stock market since 2009 can be chalked up to the Federal Reserve’s attempt to create a ‘wealth effect’ through higher stock market prices. This only exacerbates the downside risk. Why? The stock market no is longer a lead indicator for the economy.