I have also been wondering about why this benefit isn't being discussed more. We can hardly move without being bomabarded by the next big thing to "save the planet" and yet a device, which if utilized to the best of its ability can really make a difference in the world's paper consumption, is not even being advertised as environmentally friendly.
I have shown the reader to my grade 7 students, and discussed the environmental benefits, the economic ones (cost of university texts etc) and the practical ones (ease of use, fewer books to carry around). They all seem very excited about the reader and their reaction alone leads me to believe that e-readers are not simply marketable to avid readers but that there is a huge market among university and high school students (that is - if/when the textbooks become available and if/when the price of the readers is reduced considerably).