BBC Radio 4's Analysis: Protecting Privacy was broadcast on Thursday, 5 August, 2004 at 20:30 BST.
Is your mobile phone switched on? If so, a stranger knows where you are.
Mobiles are now being used to track people - not just wandering children, but employees who claim they are working from home or stuck in a traffic jam.
Use a credit card, get caught on a speed camera, or walk into a shop with close-circuit television and you leave a data trail behind. And ever more powerful computers can process all this data to discover more and more about how we lead our lives.
So where does all this leave traditional ideas of a private life, protected from the prying eyes of state or business?
In this week's Analysis, Frances Cairncross will be asking whether we should worry about the intrusions into our privacy that are the price of being connected to so many electronic networks.
Among the interviewees are those running businesses making the most of new tracking and Internet technology, those trying to regulate privacy for government and privacy experts from the US as well as the UK.
Presenter: Frances Cairncross
Producer: Chris Bowlby
Editor: Nicola Meyrick