HuffPo:

As top Federal Reserve officials debated whether there was a housing bubble and what to do about it, then-Chairman Alan Greenspan argued that dissent should be kept secret so that the Fed wouldn't lose control of the debate to people less well-informed than themselves.

"We run the risk, by laying out the pros and cons of a particular argument, of inducing people to join in on the debate, and in this regard it is possible to lose control of a process that only we fully understand," Greenspan said, according to the transcripts of a March 2004 meeting.