If you are creating public web sites and anonymous users have access to the site all anonymous users will have read access. By default this means that all users can also access the application and forms pages like for instance the allitems.aspx of the pages library. Now it's true that you would need to know the url to get there, but it still doesn't look very professional.
Microsoft felt the same way and has thought of a solution for this, the ViewFormPagesLockDown. Donald Hessing has written more about it on his brand new blog. Check it out!