I'm very impressed with both Google's and Archive's implementation of privacy considerations.  Upon marking a site private, I am immediately presented with this:

Robots.txt Query Exclusion.

We're sorry, access to http://murrayhillroad.blogspot.com has been blocked by the site owner via robots.txt.

You may want to:

Read more about robots.txt

See the site's robots.txt file.

Try the page on the live web: http://murrayhillroad.blogspot.com

Search for all pages on the site murrayhillroad.blogspot.com/

Try a different page address, at top

See the FAQs for more info and help, or contact us.

Snipets are still available in Google search results, but requests of the cache are denied.  Bravo.  I'm sure records are still kept forever, but they at least require a court order.