Apple used to use Skyhook Wireless to do geolocation on wifi devices to assist with GPS.
Now, according to their recent location services press release, as well as previous iOS release notes, they switched to an internal service to handle this. The recent PR said that they do still collect some of this information for their anon database.
Due to some changes in my wireless network (adding another base station), Find my iPhone isn't as accurate at my home anymore. It used to be very precise (could tell which side of the house a device was on), but now it shows the device across the street or in the trees.
Is there a way to manually update or refresh this location information? You used to be able to go to skyhooks website to enter your location and MAC addresses, but since Apple doesn't use that anymore - thats not helpful.