GPS tracker discovered on car

A new surveillance technique consists of placing a GPS tracking device on a person's car.  In some jurisdictions, a search warrant is not needed because the use of the device is regarded as the same as just following someone by car.  Click on this link to read a Sarasota Herald Tribune article (10-17-10) about a 20 year old computer salesman with a Middle Eastern name was shocked to discover such a device attached to his car.  He had apparently been tracked electronically without his knowledge.  Do you believe a search warrant should be required for such tracking?