The idea is that you could sell, lend, give away your book if you wanted to. Basically everything you can do with a paper book
The reason that paper has hung around so long is that, yes it's extremely versitile, but it's also in very wide usage.
If SD cards, for instance, were to become the de facto standard (due to wide usage) for a solid state ebook, then that very standardness would enforce a certain amount of longevity on the format. Think about it, how much is now still on paper because it's always
been on paper?
Books don't typically need that much actual storage space, so there's not really much pressure to upgrade to a denser format, 2Mb would do for most books, and there are 4Gb cards out there -- we wouldn't outgrow the media's capacity for a while with just books.
I'm not saying that this is a perfect solution, only that it seems to have enough merit for further consideration.
