http://www.kk.org/cooltools/archives/002538.php
New versions of Adobe Acrobat apparently support adwords-style context-sensitive ads (!), and so Kevin Kelly has released a version of his book True Films as a free download as an experiment. This method of paying producers for content may work for some content, if the ads are either difficult to get rid of, or very well-targetted (if you only see ads you’re genuinely interested in, you don’d need to opt-out of anything).