Does Yahoo use the IP Address technique that Google uses to determine the location of the individual who is running the search query? I assume they do, since you can specify a radius around a specific address in Yahoo Local Search Marketing. Can anyone answer this question? If Yahoo doesn't use the IP Address technique, how do they identify the location of a random web user (that has never registered with Yahoo) but uses Yahoo to search for products or services.
While I would certainly assume that Y! is gathering this information for other uses (why would they not?), I don't know of a current example of them using this in their search results.
To demonstrate-- do a search for the word 'plumber' then a search for 'plumber city, state'. Only the latter will trigger localized results (it should be noted, for some major metros tested the phrase ordering 'city keyword' resulted in local results, but these seem to be hand-picked by Y! and don't work for most terms/cities).
As far as I know, Y! is still matching known cities, neighborhoods and zip codes to the radius selected by advertisers, and matching to the geoqualified search phrases that occur (in the proper format).