I'm not sure if moderators have the ability to edit posts (and therefore change the subject line), but I don't think this would be a good idea anyway. Having a bunch of topics named differently today than they were yesterday could become annoying.
I just made a post in the two busiest forums titled "Posts with poor subject lines may be deleted", so that no one can say they weren't told. Perhaps a "use the forum search function" sticky post is next, although I've never been fond of forums that have multiple sticky posts at the top before the new posts start

Regarding the FAQ issue, it was meant to be addressed by the FAQ section of the forum, although I'm not sure how well it has worked. It depends on the motivation of people to create new topics, but helpers already have their hands full in other sections of the forum and probably feel people won't look at the FAQ anyway.
One thing I don't like is having one FAQ on the main site and another in the forum. A one-stop solution would be better. The forum model seems superior since it allows each entry to be replied to and given more dynamic, wiki-style updates. So I've been toying with the idea of moving the main FAQ to the forum. Hopefully this would give it a boost
