Forum Search Engine Indexing
 

What''s the go with this?

If I post an article on the CMS page Google indexes the article within a couple of hours, and they rank pretty highly too, same with Blogs.

I have seen spiders in threads but threads never get indexed, not one.

I have 10 forums sections on the site but only 3 are accessible to visitors, with the other 7 you need to be a member to read them, could this be the reason why the threads in the 3 public accessible forums aren't being indexed?

I have basic friendly URL's set and I am curious as to why the articles and blogs are so successful at being indexed but not the threads. Any clues?