I think you're missing the point. The argument isn't that bloggers as a whole perform better than professional analysts, it's that there are far more sources to get information about the market these days than just Wall Street analysts. Bloggers are one of them, and there are times that they are right.

Some blogs are about as reliable as pecking chickens, but some spend considerable time researching and developing solid insights. Generalizing and discounting every single one is a bit rash.