>Make that 1003+ times. At least in my part of the US, even a pretty modest-size city will have multiple zip codes.

Is that an issue? Who cares that new york city has 20+ zip codes? Just fill autofill "new york city, new york".

>for example, some zip's are just for Post Office Boxes.

Again, is it bad except for some joker who wants something sent to an invalid address?