Alot of the guests are bots from google and yahoo. I do have a mod setup were visitors can only view 4 or 5 threads until they have to registering to view more. The lab talk forums are all private and also the polls.
A couple new things I am working on are a photo album for pictures
Dental Lab Network - PhotoPlog - Gallery
and a review section for members to post reviews on products.
Also anticipating vbulletin 3.7.0 which is in beta right now but has alot of cool features and I will upgrade once available for use.