Imagine walking into a bookshop and asking for the latest bestseller. The shop keeper runs it through the till. But before you pay he insists you sign a set of terms and conditions which allow the shop to know where you are when you read your book and track who you pass it on to.
Such possibilities seem straight out of a Philip K. Dick novel. But in cyberspace they are a normal part of everyday transactions.
The decision by the photo-sharing website Instagram to change its terms and conditions, and the consumer backlash it generated, has thrown into sharp relief just what we agree to when we visit a website, sign up to a social network, store data on the Cloud or purchase goods online.
Instagram, sold to Facebook this year for an eye-watering US$1 billion ($1.19 billion), is looking for ways to monetise - a not unreasonable request given its 100 million users get to benefit from its software for free.
For many, Instagram went a step too far when it appeared to suggest it could to sell anyone's photos to third parties without notice or recompense. It has now backed down, promising it wouldn't sell your photos.
The damage may already be done. Meanwhile, people are asking, just what is it I've agreed to on all those other apps and websites I use?
The fact is that when we visit websites, sign up to online communities, buy apps and goods, we are often asked to sign terms and conditions which effectively treat the consumer like statistical guinea pigs. Very few of us even bother to read them.
Personal data collection is particularly lucrative when it comes to mobile technology. Recent research by the United States technology firm Juniper Networks found 24 per cent of free apps in Google Play, the app store for Android phones, had permission to track your location. And 7 per cent could access your phone book.
But such data are what make these apps work so well. Google Maps needs to know where you are to guide you to your next destination. But legitimate concerns exist when that information is given to third parties.
Most of the major online music retailers, such as Apple and Amazon, are not selling you a music file when you download it. They are selling you the rights to listen to and distribute the file as laid down in their terms.
We might collect thousands of films, books and song tracks. Yet under most of the current terms we can't pass them on when we die.