For decades, authors have used page numbers (and book/journal titles & editions) to refer to other works. With the advent of epublications and ereaders, it seems that our previously printed page numbers no longer serve a clear reference purpose, because when a reference to a particular page is checked on an ereader or tablet it somehow no longer makes sense. Where is this illusive page the author mentions? How can I see what the original page from a printed work was? Not all ereaders support the display of the original (print) page number, and when they do, it is up to the creator of the epublication to have supplied this information in the metadata of a work.
Amazon of course, in their native Kindle publications, has started using locations and (print) page numbers as so-called place holders, but these seem to exist more to facilitate the continuation of reading a text than as a identifier for future reference.
The other day at work I was talking to a colleague about this lack of reference identifiers. We work for an international academic publishing house and we are anxiously reading up on all the latest EPUB3 technologies, because we believe it to be the future of another form of publishing. As it happened, we started thinking about creating identifiers to sections in a text which could in turn be used to accurately locate content when referring to it.