The stock market has been dishing out more stiff lessons than a cranky schoolteacher back from summer break. Five months after what just about everyone figured was a bottom, stock indexes are plunging anew. Last week the Standard & Poor's 500 dipped below its April 4 low, and it has now erased more than three years' worth of gains. The NASDAQ and Dow are flirting with their April lows too.
Facing a second consecutive year of losses, thunderstruck hordes of investors have begun to move serious money out of stocks and into bonds, money-market funds and savings accounts. That's not quite...