This article covers anonymous placements.
Anonymised URLs are being deprecated for the Google Display Network, in order to be compliant with Ads.txt requirements. Going forwards, the results discussed in this article will become outdated. Learn more about the deprecation.
After we deprecate anonymous placement targeting and reporting, no advertiser should see placements marked as 'anonymous.google' in the results. Some publishers choose to offer placements anonymously and don't disclose their site names to advertisers. Even though the publisher and website remain anonymous, you'll still have access to reporting statistics from the ad placement.
If you choose to place your advertisements on anonymous publisher inventory, you agree that any image and reputation standards that you may have for those publisher(s) are sufficiently addressed by the policies that Google enforces against publishers.
If publishers violate these Google policies, then Google has the right to take action against those publishers, including, without limitation, removing those publishers from Google's services.