And I was talking about the value of that 'more business' which comes from Game Mechanics. Whether you're trying to sell sneakers, services or page impressions, changing the user's focus on the site will necessarily change their behavior. Which will cast doubt on the applicability of your old knowledge of how the site works.

Suppose you're trying to sell shoes and you notice that shoes with reviews sell better. So you add a karma reward system to incentivize reviewers.

The very act of soliciting those reviews with rewards will be reflected in the average review. And the relationship you formerly noted between reviews and sales, may no longer hold true. It may have been that the former relationship was truly between informative reviews and sales. And your reward system has created a flood of preference reviews which don't have the desired effect.