You can easily remove seeds from appearing on their public collection pages on www.archive-it.org (ex: http://www.archive-it.org/collections/866). In our web application, navigate to the "Seeds" tab of any collection. To edit the public accessibility of one seed, click on it's hyperlinked URL; for multiple seeds, check the boxes to their left and click the "Edit Settings" button at the top. Both methods will take you to an interface with a check-box marked "visible to the public." Un-check this box and click the "Save" (for one seed) or "Apply" (for multiple) button to make your change.
For advanced guidance, including alternative methods of restricting access to your archives, see: How to restrict access to your web archives.