I got this great question in email and wanted to post it here.  For the ListingManagement web services, ServiceArea is a set of enumerations that includes city, zip radius etc.  What is the location that determines what city, or zip code or state to use as the basis?  This is actually the address of the listing you created.  So if your listing address is San Francisco, and you set the service area to be city then it is San Francisco.