I always wondered if integrating one forum/site with another would help or hinder that site in the long run (never done it myself! ). It can be frustrating when you're a member of one site and suddenly you're thrown into another. From an admin's point of view it's certainly nice to be able to add all these "new" users and content to their forums/sites, but the impact on SEO and the work required to balance this is a pain It is not difficult to imagine that themselves.