It appears Google Germany has removed many, if not all, adult video sites from their index. A Google Groups thread reported this, where an adult video site owner said his Adult Tube site was removed from Google.de and so were all his competitors.

Googler, JohnMu, explained that a site command for at least one of the sites, such as site:www.redtube.com, returns a message from Google that it was removed due to local laws.

If you click over to ChillingEffects.org it explains:

The same with other sites, such this message, “German Court Order against display of privatamateure.com and youporn.com.”

Forum discussion at Google Groups.