ZH have spotted an interesting set of FOMC minutes from 2008 with comments by Janet Yellen and Ben Bernanke:
““As Japan found during its quantitative easing program, increasing the size of the monetary base above levels needed to provide ample liquidity to the banking system had no discernible economic effects aside from those associated with communicating the Bank of Japan’s commitment to the zero interest rate policy.”
When does QE 4 start?