Hi
We import shape files in to the warehouse of countries, counties, nature reserves, lakes etc. These allow us to provide reports of records within those areas. The shape files are usually produced by the institutions that want these reports. We have quite a lot for the UK now.
We have used Yahoo services for quite a different thing; allowing a user to type a place name and zooming the map to their location. The service provided geocoding - converting a place name to a latitude and longitude. We have switched to a Google service which provides the same function.
Hope that helps,
Jim Bacon.