The conventional reply is that noise traders improve markets by making rational prediction more profitable. This is almost certainly true for short-term noise, and my guess is that it's false for long-term noise, i.e., if prices revert in a day, noise traders improve a market, if prices take ten years to revert, the rational money seeks shorter-term gains. Prediction markets may be expected to do better because they have a definite, known date on which the dumb money loses - you can stay solvent longer than the market stays irrational.
I was very interested in the discussions and opinions that grew out of the last time this was played, but find digging through 800+ comments for a new game to start on the same thread annoying. I also don't want this game ruined by a potential sock puppet (whom ever it may be). So here's a non-sockpuppetiered Irrationality Game, if there's still interest. If there isn't, downvote to oblivion!
The original rules:
Enjoy!