It's not public.... Well, it's nominally publicly available, but it's somebody's searches, interests, and social media activity gathered up by those companies—shielded because the service is offered for free—and then packaged and sold to consumer companies. We all know that if we type “shoes” in Google, suddenly shoe ads start appearing all over the place. There is no protection of that particular data being sold further on, is there?
On February 16th, 2017. See this statement in context.