I really like this story of the unanticipated effects of the printing press from Steven Johnson:
Once people started to read, and once books were in circulation, very quickly the population of Europe realized that they were farsighted. This is interestingly a problem that hadn’t occurred to people before because they didn’t have any opportunity to look at tiny letter forms on a page, or anything else that required being able to use your vision at that micro scale. All of a sudden there is a surge in demand for spectacles. Europe is awash in people who were tinkering with lenses, and because of their experimentation, they start to say, “Hey, wait. If we took these two lenses and put them together, we could make a telescope. And if we take these two lenses and put them together, we could make a microscope.” Almost immediately there is this extraordinary scientific revolution in terms of understanding and identifying the cell, and identifying the moons of Jupiter and all these different things that Galileo does. So the Gutenberg press ended up having this very strange effect on science that wasn’t about the content of the books being published.
As I’ve established here, I’m a big McLuhan fan, and this is pretty good evidence that the effect of the medium is often much more important than the specific message.