I agree with the people who are posting about the very small percentage of people who get actively involved in online community (or any form of community).

We found similar problems with our "Katrina's Jewish Voices" archive, where we are getting scads of information through organizational connections, but get relatively few online contributions, and very few people tagging items that aren't there own contributions, tagged when uploaded.

Our feeling is that the solution is to find more ways to involve people over time, including the building of specific sub-communities (educators using our materials, for instance, in our case). Eventually, the number of overall participants from whom our small group of active participants comes, will grow. In addition, there will be the William Whyte network benefit--people like to be where people are (this was in answer to the original question, "why do people stand and talk in the middle of traffic on a busy streetcorner instead of moving to nearby benches or alcoves"). So, the more discussion and activity that there is, the more that there will be. We hope.