The Song-Beverly Credit Card Act of 1971 (Credit Card Act) (Civ. Code, § 1747 et seq.) is a California statute that prohibits businesses from requesting that cardholders provide "personal identification information" during credit card transactions, and then recording that information.
Yesterday, the Supreme Court of California reversed prior decisions and included a person's zipcode in the definition of "personal identification information" in a case where Williams-Sonoma asked for such information during a credit card transaction and then used such information to do targeted advertisement. The Court made this holding while agreeing that a zip code was not unique to any particular person and that many people had the same zip code.
It is likely that the fact that the merchant recorded the information and then used it to deduce the customer's address played a big part in the Court's thinking. Had the merchant merely requested it and then not recorded and used it, the result may have been different. Under this reasoning, area codes, cities and counties of residence and other means of identifying the general area of personal residence could also be so classified and this would seem to be somewhat extreme.