Fair use is incredibly profitable
Amazon just sold me on a $75 book based on a single diagram (above), seen in the online preview for the book. The title is The Semantic Turn: A New Foundation for Design. It looks pretty damn salient to my current train of thought.
I found the book through a citation in an academic paper found with Google.
Publishers who are afraid of having their books and papers indexed, and previewable online, are idiots.