Face recognition, behaviour analysing surveillance cameras, biometric profiling and the monitoring and storing of our shopping patterns has made snooping into our habits, movements and private lives ever easier.

Dismayed at its shrinking power to market to us via traditional media or even the internet, the private sector is now proposing to reach potential customers in ways that critics say should have us all concerned.

"There is an enormous pent-up demand for personalised location advertising, whether it is on your cellphone or PDA, on your radio in your car, or on the billboards you walk by on the streets and inside stores," says Bruce Schneier, chief security technology officer of BT.