All my rich friends sold too early

This is a favorite saying of a dog walking buddy which might apply to the bond and equity markets of today.

As soon as investors get a clear signal that the Fed will slow down its money printing operations, some, like David Stockman, expect the market to fall. 

Notoriously pessimistic (but very funny) Zero Hedge thinks we have already received four signals that we are in bubble territory.
Of course, bubbles are phenomenon that cannot be understood by economic models, and by logical extension, economists, so my credibility here is low.