For a while I was answering "90210" when asked by store clerks for my zip code. The reactions ranged from laughs to scowls. Eventually I started providing the same zip code as the store.
If you are wondering why stores aren't so insistent about our zip codes these days it's because some class action lawyers in Boston have been suing retailers over this. There's a story about that at BostonGlobe.com. The link follows this excerpt:
In the past two years, at least 25 retailers have been sued for more than $100 million for requesting ZIP code information from Massachusetts customers. Most of the lawsuits have been settled or withdrawn, but the practice of asking customers for their postal codes — bits of information with a marketing value of perhaps 5 cents each — has cost retailers millions of dollars in settlements and attorneys’ fees.
Preston Leonard, a Boston lawyer who has filed class-action lawsuits against companies including J. Crew and Brooks Brothers for collecting customer ZIP codes, said that retailers don’t ask for postal codes to make sure the person swiping the card actually owns it. Instead, he said, they use the information to confirm shoppers’ addresses and then bombard them with junk mail.
“A lot of people think it’s required as a condition of completing the transaction, when it’s not required by the card companies,” Leonard said. “The idea just generally is to gather as much data about the consumer as possible.”
Here's the link: Mass. retailers ask for ZIP code, and lawsuits follow. But be forewarned that the site will tell you you can read five articles for free before you have to subscribe. Further, as with any other website, it will attempt to collect as much information about website visitors as it can.