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.