I doubt there are many case histories, but I have discussed this idea before. Since it was not made specific I'll refer to two situations.

-- How do new forums attract members and posts. Differentiate. Be narrower in topic but explore more facets. Take on old topics from new perspectives and write it up as innovative forum section titles. For example, content driven design is talked about. When you see the threads here, discussion quickly reverts to linking-centricity, construction-centric or technology centric perspectives -- everything but a content-driven perspective. Content is the most-talked about, least understood topic in web design.

One forum, for an HTML editor, switched and wiped out all the previous posts. This discouraged the existing members who left, forcing the operator to start from scratch. That forum never recovered, and it has been some two or maybe three years now. They were under the mistaken impression forums produce content automagically, not a surprise if you develop HTML editing software.

-- Add Content. Don't fake posters. Go to other forums, seek out popular topics, and make them into a FAQ. Seek out people with specific points of view and entice them to post. Or go to an article dump with specific rights to republish, follow the publishing guidelines, and republish them. If you randomly dump content, that will be signalled to potential forum members. If you select those article you feel represent quality, a different signal will be sent.

-- Established forums can experiment with community-building. This means Moderator guidelines. I was just at a forum who had a sudden influx of new members -- a mass exodus from another forum. Turns out some arbitrary actions by one mod constituted a policy change which alienated all the core members. This relates to the next idea...

-- Identify and retain core members. Segment them. For example there may be Advisors, who hardly ever initiate posts, but prefer to help others with problems or questions. And Producers who come up with off-beat, innovative posts, topics, and perspectives. Find ways to nurture, support and reward these segments.

A forum is just as much a publishing platform as a newspaper or blog site. A forum is also like managing a social or nightclub - a people business. (And I wish it wasn't compulsory to add and emphasize emphasize this obviousness, but it is.) Consequently, it's hard to find less of a concentration on the reason people become interested in the forum: Content part and parcel of which is the content of the Community.

Digital economics make it easy to start up a forum or blog, with standard infrastructure. This lowers the barriers to look-alike me-too competition. Such a system rewards innovation and imagination, and penalizes cookie cutter sites. Information isn't the same 500 posts repeated, with minor variation, on 20,000 forums.