Computerworld Article: "Microsoft takes on Google with Virtual Earth
Web service and international versions on the way
Through a client application called Microsoft Location Finder that can be downloaded when a user clicks a "Find Me" icon in Virtual Earth, Microsoft accesses the MAC (media access control) addresses of wireless access points that a user's device can reach, whether or not the user is logged in to any of them, he says.
Microsoft has worked with third parties to assemble a database of router MAC addresses and the latitude and longitude of those access points. Location Finder finds the access points in the database and then triangulates the location of the user's device based on the signal strength of those access points, Law says."