Zip+four is only down the the block level, you need 2 more digits (zip+6) to uniquely identify every possible address in the US. That said, a 9 digit barcode is way too close to a full address for most people to be comfortable with sharing online.

I suppose I grew up semirural, so growing up, my zip plus 4 identified my single house. Good to know that's not thexactly the case all the time. Still, pretty identifying.

It narrows it down to a delivery truck at least.