Google announced the change on its Inside Search blog on 10th Aug 2012. "Starting next week, we will begin taking into account a new signal in our rankings: the number of valid copyright removal notices we receive for any given site."
The effect: "Sites with high numbers of removal notices may appear lower in our results."
Google gave the scale of the notices it was receiving: "more than 4.3 million URLs in the last 30 days alone", more each day "than we did in all of 2009".
It also drew a line around what the signal was not. "Only copyright holders know if something is authorized, and only courts can decide if a copyright has been infringed."
Google never called it Pirate. Its ranking systems guide today describes a "removal-based demotion" system that uses removal signals to demote sites, the descendant of this change.
