In my opinion, the greatest influence over stock prices does not come from public message boards.  Posters in these places are of two types - those seeking information (or wanting to share it), and those wishing to influence the direction of the stock price.  In the second case, those posters who think they can move markets to their advantage are only fooling themselves.  Sometimes they get lucky with a coincidental move, or simply ride a trend bragging/implying all the while about their brilliance.  Responding in any way only encourages them.