The New York Civil Liberties Union doesn't have a problem with private companies using GPS technology, but it did express concerns over the city’s proposal to fit cabs with the GPS system.
"Once the government starts tracking people's whereabouts, it starts raising concerns," said Chris Dunn, an attorney with the rights' group. Taxi drivers apparently agree, and protested outside the taxi commission offices last month.

Mafioso and carjackers aside, you might have legitimate reason to be concerned. This does raise the prickly issue of what taxi cab companies (and other companies who utilize GPS technology in their workplace) will do with the tracking data. How long will they retain it? Will it be kept secure?  Are we going to see a Sarbanes-Oxley type requirement for GPS data retention? On the plus side, next time you’re in a whiplash related lawsuit, you’ll have the data to prove the taxi was speeding. Love it or hate it, GPS technology is quickly becoming a part of modern life.

More details available via SiliconValley.com