Some sites block their members profiles, some block the "Off Topic" area of their forums, some block all non niche related content, some block nothing.
On your sites, what areas do you block search engines from indexing? Why don't you index those areas?
If your guest can't see it then search engines also can't see it for it to be indexed. Makes sense right. Most all boards/categories are indexed apart from the trash tin and the staff boards.
I mostly just block search engines from scanning folders that they don’t need to (ex; /images since any image will be directly linked on a post or page).
Blocking them from scanning forums makes little sense since they can still tell and rank your site using that content, but marks it as less content overall due to skipping those pages/content
