Invalid zip codes in classifieds..

I frequently find that people attempting to sell equipment in AG classifieds enter invalid zip codes. Is this some kind of sales tactic or do people not know their own zip codes? I get more excited about buying stuff locally so I look at the zip if it might be close and it is not uncommon to find invalid zips. What gives?
This has been discussed before. I wouldn't say the zip codes are invalid. I would say the system audiogon uses to view zipcodes is outdated.
when I encounter this problem I just click on the Google link and it will show you a map where the zip is.
This happened to me with Bbqdrew, he lists at 94501 (CAL.) but ships from Ill. and not in a shipping center. I thought I'd get some cable in 2-3 days,instead it took well over a week. when I questioned him he just didn't answer my e-mails.
The question is why doesn't Audiogon update their database of zip codes? How hard could that be?
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I used to update the national online zipcode file at a major retailer. Each zipcode represents a post office.
Post offices open and they close or are merged so the master list always changes.
It's up to the seller to validate the zip specified in the ad (but dude! I'm so tired!).