Before you roll it out, you may wish to talk to a friend of mine. kmself at ix dot netcom dot com helped design the system used at http://www.kuro5hin.org, and did some research then on goals vs results of different moderation schemes. He may have some worthwhile thoughts.

To answer your previous point, there is a lot of difference between the value that people have realized from use of a site, and the value that they have from the potential to use it. Measuring either is hard, and my belief is that the most effective way to maximize the value of the potential from what is in the site lies in the search engine, not the moderation system.

As an example I would point out that http://www.google.com is the single most effective tool that I know of for increasing the value that people get out of knowing that they could access information that they have never (yet) looked at.