Google has filed a patent application for estimating locations. Erik Sherman has a story at bnet (beware of pop-ups) speculating what they will do with this technology.

http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.html&r=1&f=G&l=50&s1=%2220100020776%22.PGNR.&OS=DN/20100020776&RS=DN/20100020776
http://industry.bnet.com/technology/10005017/google-trying-to-deduce-wireless-location-info-bypass-carriers/