Since going off the gold standard in 1971:
Reagan realized that you can juice the economy by running huge federal deficits, thus creating the first stock market bubble since the depression.
Greenspan realized you can juice the economy by destroying price discovery of interest rates and dropping real rates negative indefinitely, thus creating the greatest housing bubble since the Japanese bubble destroyed Japan's economy.
With the deficit ballooned out of control and nominal rates at zero, Bernanke realized that you can juice the economy by printing unlimited amounts of money for ever and just giving to the banks to prop up the risk markets. This has created the dual bond and stock market bubble of 2012.
With deficits permanently out of control, rates at zero, the printing presses cranked to full throttle, when this bubble finally pops what's next?
Think of something.
I can't think of anything but gold.