tracks that we could hear just by snapping on the radio: it was
because 80 percent of the music ever recorded wasn't available
for sale anywhere in the world, and in that 80 percent were all
the songs that had ever touched us, all the earworms that had
been lodged in our hindbrains, all the stuff that made us smile
when we heard it. Those songs are different for all of us, but
they share the trait of making the difference between a
compelling service and, well, top-40 Clearchannel radio
programming. It was the minority of tracks that appealed to the
majority of us. By the same token, the malleability of electronic
text means that it can be readily repurposed: you can throw it on
a webserver or convert it to a format for your favorite PDA; you
can ask your computer to read it aloud or you can search the text
for a quotation to cite in a book report or to use in your sig.
In other words, most people who download the book do so for the
predictable reason, and in a predictable format -- say, to sample
a chapter in the HTML format before deciding whether to buy the
book -- but the thing that differentiates a boring e-text
experience from an exciting one is the minority use -- printing
out a couple chapters of the book to bring to the beach rather
than risk getting the hardcopy wet and salty.

Tool-makers and software designers are increasingly aware of the
notion of "affordances" in design. You can bash a nail into the
wall with any heavy, heftable object from a rock to a hammer to a
cast-iron skillet. However, there's something about a hammer that
cries out for nail-bashing, it has affordances that tilt its
holder towards swinging it. And, as we all know, when all you
have is a hammer, everything starts to look like a nail.