I've found that my weakest bets on fundamentals are with tech stocks. With anything else, I'm right as much as I expect to be - about 50% of the time.

With tech, I find I'm much closer to being wrong 80% of the time. I think our knowledge of the industry makes us believe we have more information than everyone else, and thus that we're in a better position to make bets. In reality, the things we know that your average investor doesn't aren't as crucial to the bottom line.