I think there is a subset of users who interact with text far more than others. I find I can't read without a pen in hand — if I am not marking up the text or taking marginal notes then I feel like I'm only receiving a narrow sliver of what I consider a "full" reading experience. (This is true for novels as much, if not more, as it is for non-fiction.) My suggestions were to bring to the Kindle something akin to the experience of reading paper with a pen in hand.