I'm sure the moderating style has a lot to do with the lack of usage - it's so heavy-handed and inflexible. I've convinced people to use the forums, they've made a post, and then it's been deleted as spam because in the eyes of the moderator it's off-topic, or if they've posted an idea it's been closed and they've been told it's not in format, and the thread closed. I've been a moderator of a commercial magazine's website now for nearly 10 years, and we have a much more relaxed style of moderating, aimed at promoting people actually using the site.
Sure, the mods here enforce the rules, but they enforce them incredibly strictly and without thought of trying to encourage forum usage. IMHO, the spam definition here is utterly absurd. There are some topics where it makes sense to enforce threads staying on-topic - ideas, yes, bugs, and specific questions - but when we get into top 12s etc, so long as the debate remains reasonably pleasant, who cares if it's strictly on topic? Let it drift a bit, let conversations develop, and people will feel more at home here - and thus use it more.
And when it comes to ideas, instead of just closing them if they're not formatted, give a link to the instructions - it's only a matter of having a standard post in the Mods' area that you can cut and paste, but it makes the experience more user-friendly. Sure, if they don't come back and format it in a reasonable time, close it, but the mods should be there to help users and use of the forum, not discourage it. This is a great example - why did nobody tell Druvi he would be risking a ban with an MM like this? Fair enough if no mod had seen it, but they had. And given they had, and hadn't commented in advance on such an outcome, it's a poor show to then say the ban was deserved and right - guys, you let him down there.
In short, I think a less gung-ho approach to moderation would result in forums that were more lively.
In-game moderation is another matter; in general, I think it works a lot better, and probably needs to be more rigid than in the forums, but there has to be more transparency on exactly what a ban is for, IMHO.
I always try to encourage people to come on the external forums from Ingame, but the majority never do...