No. Prices of financial assets can certainly rise to unsustainable levels due to overly optimistic forecasts. And this is actually pretty easy to spot, at least near its peak. You may recall that plenty of market commentators and academics spoke of an Internet bubble in the late ’90s and a real estate bubble in the last few years. What I am saying is that just because asset prices may vary greatly over time (say NASDAQ at over 5000 in March 2000 and at about 1100 two and a half years later) doesn’t mean that markets are inefficient. It just means that public information (i.e. market sentiment and forecasts) changed.