THERE IS no point in hiding. As long as it's on, your cellphone knows where you are, and it might not mind who it tells.

Kevin Bankston, a lawyer for privacy advocacy group the Electronic Frontier Foundation in San Francisco, is well aware of this. Since late 2005 he has been trying to thwart secret attempts by the US government to access users' cellphone tracking information without a warrant.

With the help of a few concerned lawyers and judges, Bankston has made headway. But now he has something else to worry about. He says that a raft of emerging technologies known as location-based services, or LBS, may make people more vulnerable to government spying than ever before. Earlier this year, he publicised details of his worst fears at the Where 2.0 conference in San Jose, California. Meanwhile, police departments and lawyers are increasingly relying on forensic ...