You will see in the Advertising System options (VBulletin options) something like this limit who sees the ads:
Do NOT display Postbit advertisements to Usergroups:
IDs of the usergroups who will not see the Postbit advertisements, separated by |
Just add the usergroups id who you do not wish to see the ads, there is also something similar below to explicitly show the ads to certain groups.
You will see at my site
http://www.thecodecage.com/forumz that you can see the ads but other members who belong to different usergroups see ads in different places to you the unregistered user.