There's a very interesting -- non-technical! -- article The Social Life of Paper that has a few words about our attachment to paper. For me this attachment manifests itself with tech manuals as a notion of 'thumbspace'. That is, I couldn't tell you to save my life the chapter where the Owl discusses how Perl's 'g' modifier works. But my thumb is smart enough to get within a couple of pages on the first try. No need to remember a page number, or flip to the index, it's just there. For me, pixels have a very hard time capturing that: no sort of searching front end you bolt onto a text can be as intuitive as this. (This is also why I'm reluctant to get new revisions of texts I consult fairly frequently -- need to train the thumb again...)

Chris
M-x auto-bs-mode