One hopes that what he pretended was a joke will follow Fed Chairman Ben Bernanke for the remainder of his days, and will be the one line accompanying his picture in some future textbook on what not to do.

"The problem with QE is that it works in practice but it doesn’t work in theory."

That just happened. Bernanke actually said that Thursday in his last planned public remarks as head of the U.S. central bank.

He was joking about critics, but one wonders exactly how well it works given printing $1 trillion a year for four-plus years running hasn't provided the recovery that he promised every year, like clockwork. And then there is the chronic unemployment (if properly measured by U6 and not U3), and stagnant wages.

There is also a general lack of productivity that even Bernanke himself admitted today that he doesn't understand. 

So he doesn't understand how QE "works" but he's willing to bet $4 trillion on it. But at least it's not real money.