In a recent California case Pineda v. Williams-Sonoma, S178241 (Cal. Supreme Court; Feb. 10, 2011), California retailers have been banned for requesting Zip code information when processing credit card transactions.
Plaintiff made a purchase at Williams-Sonoma and when she went to pay, the cashier asked for plaintiff's ZIP code. Thinking she was required to provide it in order to complete the transaction, plaintiff provided it.
Plaintiff sued under the Song-Beverly Credit Card Act (the Credit Card Act) which prohibits a store that accepts credit cards from:
request[ing], or requir[ing] as a condition to accepting the credit card as payment...the cardholder to provide personal identification information, which the [store] records upon the credit card transaction form or otherwise.
Regardless, for all of you California retailers, no more asking for Zip Codes.