@xssfox oh yeah, I recently ran into somebody else's analysis done on a zipcode (US postcode) basis. There are single-point postcodes, single-building postcodes, etc. They change and move wildly
The USPS says: zip codes are mail routes, not polygons, don't try to use them for anything that isn't mail routes, it won't with great. But the US Census publishes shapefiles of zipcodes, but missing the weirdest single point ones and modifying others to be more poly-ish, because people are gonna anyway.