The problem is enticing people beyond the Registration page. If they can't seen what's to be gained, they won't register. I disagree with what you're saying. I acknowledge your references to some vague A-Level or BSc business course, but, in the context of a fansite, I am adamant that you are not correct. If I was to select General Discussions as member-only for a week, would we see the number of posts increases? (Rhetoric) Probably, but at what cost to our attractiveness as a lurker-friendly forum. (Let's not forget that we have a ratio of about 100:10 in lurkers:registered. They might sign up, but would they post?
I might go so far as to say that I might give this a try for a week or so. The logic is quite sound, and chances are we wouldn't actually lose out. At least not in GD. Present me a sound case in your next post and I'll respect it enough to at least try it out in the most eclectic forum.
You might be a cunt, but I'll still attach some value to what you say. We've been through a lot.