The BBC World Service’s Monday Documentary series Virtual Revolution radio adaptation continues today at 1005 GMT, with The Cost of Free, a look at the exchange we make for free services like Google and Amazon.

Here’s the blurb:

The World Wide Web has transformed retailing, communications, and social lives, with sites like Google and Facebook now household names. What’s more we take it for granted that most such sites we visit are free of charge. But does “free” come at a price after all? In this week’s edition of “The Virtual Revolution” Doctor Aleks Krotoski considers the implications of a commercialised web for privacy – finding that among other things, we’re all being watched as we shop, network and send emails.

If you miss it when it broadcasts, you can catch up on iPlayer, or you can download the documentary as a podcast.