Michael Lewitt hits it straight down the fairway:

"We have been taught that bear markets do not begin until the yield curve inverts, which in turn is caused by aggressive tightening by the Federal Reserve. It is fair to ask whether this rule of thumb still applies when the yield curve and every other financial metric has been grossly distorted by five-plus years of zero interest rates and trillions of dollars of quantitative easing. Thus far in 2014, the 2/10 curve has flattened by about 75 basis points but is still steep at +186 basis points (as of October 14). Maybe markets will not require an inverted yield curve to decide that stocks should experience more than a run-of-the mill correction. Perhaps markets will decide that the failure of trillions of dollars of money printing and years of zero interest rates to create sustainable economic growth are reason enough for stocks to trade not at their current elevated valuations but at more modest levels that reflect more realistic (and lower) long-term growth prospects."