Be fearful when others are greedy and greedy when others are fearful?  Warren's famous quote -- how true is it?  If looking at the AAII sentiment data, it is dead wrong.  The best times to be fully margined long this market in the last two years were when the AAII sentiment was ridiculously bullish.  This bull parade lasted 6 weeks on average and the most bullish sentiment came near the bottom and at the start of bull runs -- not the top as many believe.  What about tops -- what happens there?  Actually, the data shows that investors are actually reigning it in and really aren't that bullish at all.  In fact, before August's big plunge, the data was skewed slightly bearish.  I have seen people lately saying that we are nowhere near a top because people are getting less bullish.  I believe this to be an incorrect assessment of the sentiment data.  I don't claim to know where/when the top is, but if you are waiting for the data to suddenly swing extreme to the bullish side at the top, this would actually be unprecedented market behavior from what I see.