tokens: Unfortunately , recent studies and news indicate the insufficiency of this method : Cases as the re - identification of AOL users from released , anonymised search queries ; the identification of individuals via correlation of common demographic data like zip codes , gender and date of birth ( ) ; or the work of on de - anonymising sanitised data from the Netflix Prize data mining contest demonstrate how the umbrella of Personal Identifiable Information ( PII ) becomes wider over time as new data association techniques ( like machine learning and data mining ) evolve .