The visible symptom:  
Attracting and retaining people who can positively participate in the community, either both asking and answering questions, or at the least providing substantive answers on some kind of "regular" basis.

This has been an ongoing issue for the site for a long time now. I'm really not sure there is an answer, or where the root of the problem lies. But there are contributing, conflated, and correlated issues.

1. People don't vote. Some people have great voting records, but on the whole SF has less votes per user-views than some other sites in the SE network.

    Contributing factors:

     - Our subject matter is already quite wide, and we may have relatively few experts per subject field. People may not feel comfortable voting on topics they don't fully understand.

     - Many Questions show questionable effort, and many Answers are of questionable value to the OP. It's hard to test potential answers unless you are actually experiencing the same issue as the OP, or have at some point in the past.

    Possibly Related:

     - Questions that have an answer tend not to be reviews by people who may have subject matter knowledge. They tend to be viewed only by new people having the same problem. Many of those new people aren't users, can't vote, etc. At some point in the past some SE sites had a feedback mechanism to allow non-users to indicate a post was helpful - SF doesn't have this, and it didn't affect the post scores anyhow.

    Consequences:

     - We can't rely on voting to blow away bad content. We've established a number of higher-reputation users who can Vote To Close and they patrol the review queue. This leads to a "heavy handed" approach which generally works, but leaves many new users with a negative view of the site. Also, it's extremely uncommon for anyone to leave personalized feedback about what's wrong with the post. New users seem to overwhelmingly ignore the Help Center, sidebar Help, and any other automated help of any kind (perhaps we should just lie to the users and have those messages come from "Joe Blow" or whatever - not crazy about this idea, but I don't have anything better).

     - When people do vote, the reputation of the poster seems to be weighed into their decision (people with high rep tend to accumulate more rep for an otherwise equal post as compared to someone with low rep). This means new users are less likely to receive *magical Internet points*, and less incentivised to be gamed into SF.


Meeting... I'll be back in 30-ish.