For the past few years, a massive dose of free money, thanks to zero-percent interest rates and "quantitative easing," has sparked a similar sense of euphoria in many financial markets. One shouldn’t overdo analogies, writes MarketWatch, but free money and Vicodin have one thing in common. They wear off.

It is alarming to think how much of our economic recovery, halting as it is, is simply the product of financial engineering and artificially low interest rates. What will happen when those rates go back to normal, and the Vicodin wears off?