I too am wondering a similar thing. I’d like to have a login/pass that can direct the specific user to the allowed category.
Example: I’ve got a Category of projects; Project 1, Project 2, Project 3, etc…
I want a list of users with login/pass access to Project 1 only, Project 2 would be a different user, Project 3 another batch of users, etc..
The basic concept is to have private postings via categories. This could work really cool for project updates and communications.