Skyhook provides the GPS-like location features in the iPhone and iPod Touch. It accomplishes this by a combination of Wifi and Cellular tower locations. To seed their database, Skyhook sent out teams of drivers to correlate hotspot locations with their geographic location. Over time, as Wifi base stations are moved, the accuracy can drift.
Skyhook's submission system allows you to correct these incorrectly labeled Wifi basestations.
[ via iPhoneAtlas ]