Very good point, this isn't just something that reads emails and makes random decisions though. It only saves messages from the focus groups, which are where the specilized questions are asked and answered at our company. An example would be that any email sent to the "Storm Water" internal mailing list is saved in the database. Any messages coming to the list with a "Re:" in the subject are associated with the parent message to construct a thread. Obviously message-by-message moderation is possible and helpful.
We created the KB as a place where any user could get there with one click, type in a word, and see all discussions related to it. That way they didn't have to do a lot of topic browsing or digging around. I agree that a Wiki is much nicer and can be more effective, and the KB itself is a nice complement on the discussion side of it, but for the sake of this conversation I wanted to present a workable alternative that we'd used in place of a full-blown Wiki, since there are probably other companies out there whose users might not get as much as they could or should out of an internal Wiki, as KENAT stated. Being able to suck in messages from the focus groups allows the KB to build itself through the natural course of the company's technical conversations, rather than relying on additional time and effort from the users.
Eric