The Economist takes el jefe to task.

"The deepest flaw in Mr Greenspan's policy towards asset prices is its asymmetry. If the Fed always cuts interest rates when asset prices tumble, but never raises them when they soar, then investors will be encouraged to take bigger risks. That makes bubbles more likely. The Fed was right to ease when the stockmarket bubble burst, to avoid repeating the Bank of Japan's mistake in the 1990s. But such “mopping up” should be a last resort, not a concerted strategy that cushions the bursting of one bubble by inflating another—since 2002, in housing."