Why Retailers Ask for Your Zip Code

According to this NY Times article, giving away your zip code could mean giving away a lot more than that.

It turns out, though, that stores are asking you for marketing purposes — an issue that is starting to come to light in state courts. Stores want your ZIP code because, combined with your name from your credit card, they can use it to find out other information about you from commercial databases, like your full mailing address. They may even sell the information to data brokers, who sell it to other marketers.

The result can be unwanted catalogs and other junk mail. (To get a simple idea of the cumulative impact of each tidbit of information, try searching for your name alone on Google search, and then search again using your name and ZIP code, and see how much more data comes back.)