The trick is to use the "Admin-only create actions" option in the admin interface (/admin on your site). If you put "articles" in there, then only admins would be able to create new articles. If you put "articles headers" then that would apply to both the blog and the headers. If you're not interested in using a particular section (e.g. headers) then you can also hide the tab very easily with a theme. Here's an example that hides the blog tab and makes a custom login background:
| Tue, 05 Aug 2008, 10:51pm | Blog Privs » |
|---|---|
|
|
| Offline | Link |