I think Phil Gyford’s observation here is really important:
It wasn’t long ago that buying a purely digital piece of music — downloading a file rather than paying for a piece of holdable plastic — seemed terribly modern. But already I feel like an old fool when I visit Amazon or 7Digital to pay for an MP3. These days, a several-megabyte file on my computer is starting to feel as much of a burden, as much of a physical thing to cart around for the rest of my life, as a CD or a cassette or a record.
I can imagine the Renaissance analogue: “An octavo book printed on paper is starting to feel as much of a burden, as much of a physical thing that I need to store and display and move from home to home, as a manuscript folio book on parchment.”