Why are some topics not visible until you log in?

[coredumped]

Some topics show up on the recent posts page, but when you click them and go to the forum you can't see the contents until you log in. Why is that, and what is the criteria for having a "hidden" topic?

For example, open a new private window and follow this link:
http://www.metrojacksonville.com/forum/index.php/topic,24062.msg408636/topicseen.html#new

[Lunican]

National politics is members only.

[BridgeTroll]

If I remember correctly... It is the national Politics page that cannot be viewed unless logged in.  The reason being to encourage more thoughtful debate among regular users and to help prevent the "drive by" flame war style of posting popular on other commentary style sites...