This is a nice demonstration of the information explosion, which is the best reason for privacy concerns. You hand out your zip code, probably figuring that not

This is a nice demonstration of the information explosion, which is the best reason for privacy concerns. You hand out your zip code, probably figuring that not much can be deducted from that and suddenly, they know your address, from there on they can get an idea about your income (think about rent), maybe about your general background and so on and so on. It's scary to think about it like that.