SEOBook author Aaron Wall, has switched his SEOBook product over to a subscription community. I just had a chance to sign up today (link here.) At $100 a month, its not cheap, but you get access to his training program plus exclusive SEO Forum.

I have been a member of several exclusive, paid forums as well as free private communities. The biggest downside is often a loss of momentum due to members cutting their subscriptions. Given how prolific Aaron Wall is with his blog and promoting I am willing to bet this will be a hit.