Why would you need this? You can easily define an "admin" blocks section and fill your admin-only blocks in there. Regular users don't see it as they don't have the permissions to see the block. Optionally, you can restrict these blocks to only show up on certain pages with Drupal's built-in features.

2006/8/5, Neil Drumm <drumm@delocalizedham.com>:
Dries Buytaert wrote:
>   2. a better adminsitration theme and/or

I don't think we should have a separate administration theme, but a
separate administration themeable function, in parallel to theme_page()
and theme_maintenance_page().

This could solve the blocks issue by making a hard-coded administration
block region which is only used by the administration themeable function.

--
Neil Drumm
http://delocalizedham.com/