Monetary policy has very limited effect when you are up against the zero lower bound of interest rates as the US has been for quite some time.
http://krugman.blogs.nytimes.com/2013/10/15/five-on-the-floo...
http://krugman.blogs.nytimes.com/2013/10/15/five-on-the-floo...
However, they were instrumental in the last economic crisis by fueling the housing bubble. It seems fueling bubble after bubble is something they do well. Maybe they have to to prevent the music from stopping. Or... who knows....
Count me among those who is inherently suspicious of bankers. But that could be as much bias and ignorance as anything else and I am well aware of it.