I read the same article. The idea of revenue coming in via a third party makes it clear: the website gives away information or products, the visitor gets free info or products, and the advertiser (third party) pays to be there.

And most people expect to be able to get free things online - I know I do.

The book "Free" is not out yet. I'm sorry I forgot the author's name, but it is the same gentleman who made "long-tail keywords" famous a few years ago.

Kim