Twenty years on from its invention, Dr Aleks Krotoski continues her investigation of how the World Wide Web is transforming almost every aspect of our lives. She gives the lowdown on how, for better and for worse, commerce has colonised the web - and reveals how web users are paying for what appear to be 'free' sites and services in hidden ways.

Joined by some of the most influential business leaders of today's web, including Jeff Bezos (CEO of Amazon), Eric Schmidt (CEO of Google), Chad Hurley (CEO of YouTube), Bill Gates, Martha Lane Fox and Reed Hastings (CEO of Netflix), Aleks traces how business, with varying degrees of success, has attempted to make money on the web.

She tells the inside story of the gold rush years of the dotcom bubble and reveals how retailers such as Amazon learned the lessons. She also charts how, out of the ashes, Google forged the business model that has come to dominate today's web, offering a plethora of highly attractive, overtly free web services, including search, maps and video, that are in fact funded through a sophisticated and highly lucrative advertising system which trades on what we users look for.

Aleks explores how web advertising is evolving further to become more targeted and relevant to individual consumers. Recommendation engines, pioneered by retailers such as Amazon, are also breaking down the barriers between commerce and consumer by marketing future purchases to us based on our previous choices.

On the surface, the web appears to have brought about a revolution in convenience. As companies start to build up databases on our online habits and preferences, Aleks questions what this may mean for our notions of privacy and personal space in the 21st century.

I think I would prefer to have lived my adult life in pre-internet times. I remember what the world was like before the internet took over, and sometimes I think it was a lot better.

It wasn't, though.

At least you could float a check back then.