As Jay Stanley reported last year for the ACLU, one of the earliest instances in which the powerful privacy implications of having your search history recorded occurred in 2006, when AOL released a large set of searches that had been conducted on its sites. While the identity of the searcher was replaced with an arbitrary number — so that all of the searches by an individual were still gathered around the same identifier — members of the media found that it wasn’t difficult to identify searchers’ hometowns, neighborhoods, age, sex, and other identifying details through their searches. The result was “an electrifying sense of just how intimate and revealing the information one ‘shares’ with a search engine can be.”

About a year ago, New York Times columnist David Leonhard told NPR about how search terms differ geographically, with major differences between counties where life is easiest and counties where life is hardest. A high prevalence of searches on health problems like blood sugar and diabetes, searches on “what might be called the dark side of religion,” searches about selling Avon or getting Social Security checks, and searches about “specific kinds of guns” occurs in areas where people are more likely to struggle with money or suffer health problems. Your searches give your search engine a view of how economic trends manifest themselves in your everyday life — something you may not want advertisers capitalizing upon.