treeline - 3:13 am on Jan 17, 2008 (gmt 0)

Basically nobody knows or uses the last 4 digits. They may recognize it when they see it as it's on most mail. It has appeared for years that I may have 2 zip+4's, or they're just confused. I get mail with both.

What almost everyone has that is very local is a telephone number. This is how many mass merchants keep track of customers. They tie back to a VERY local address. Well, until the cellphone started to grow so much that many people don't have a real phone anymore.

Bonus: everyone knows their phone number