If sellers had to list their area code when they list, an area code search could be added in addition to the zip code search. Your local phone directory has a map with all the area codes.
Capability to Search for Local Used Equipment
I think it would be great if Audiogon provided search capability based on location. I would like to type in my zip code and find out what's for sale within a 50/100 mile radius of my location. I just sent an e-mail to Audiogon with this suggestion, and they replied that they would consider it. If more people request this, maybe they'll do it.