They want to know my zip code so they can clutter my e-mail screen with local ads. But I see the local ads that interest me, which are specific sales ads, in the local newspaper. I don't buy local stuff online! The purpose of the Internet should be to tell me what's going on in a place where I don't actually live...such as the street address I use for e-mail accounts, which is where I used to live, still know people, am likely to revisit, and would like to be alerted to ongoing sales if I were planning a trip.
The ads for Internet dating services are especially clueless. They're keyed to the public access computers I use rather than my e-mail, so they're telling me who's trying to use Internet dating services in my home town. More than half of the 2500 people in this town are related to me. If I were looking for a new Significant Other, which I'm not, I would not want to be introduced to a bunch of distant cousins...and I'm sure that these guys aren't paying to be introduced to me. Duh!