In the online age, page/line-based quotation is obsolete (for current
and forward-going text). Pages are and have always been arbitrary
entities. A document's natural landmarks are sections, paragraphs and
sentences. That is how quotations and passages should be cited, not by
page numbers (though page numbers can be added in parens as a courtesy
and curiosity, for continuity, for the time being, while pages -- and
PDF -- scroll inexorably toward their natural demise).

It goes without saying that all quotations, citations and references
should be hyperlinked. I am sure that XML documents will be tagged for
section number, paragraph number and sentence number, so that it will
be natural not only to pinpoint the passage to which one wishes to
refer, but to hyperlink directly to it.

This answers, in passing, one faint concern about the self-archiving of
authors' final refereed drafts instead of the published PDF: "How will
I specify the location of passages I wish to single out or quote?" The
answer is paragraph numbers (or, if you want to be even more precise,
section numbers, paragraph numbers and sentence spans). They have the
virtue of not only being autonomous and ascertainable from the document
itself, but they are independent of arbitrary pagination and PDF. (It will
also be useful for digitometric analyses.)

(I introduced this rather trivial and obvious online solution in
Psycoloquy
http://psycprints.ecs.soton.ac.uk/
in the early 90's,
http://www.ecs.soton.ac.uk/~harnad/Hypermail/Theschat/0037.html
-- though I'm sure I wasn't the first --
and APA at last began recommending it in 2001:
http://media.library.ku.edu.tr/refpgs/sociology/style_apa.htm )

http://www.google.com/search?q=harnad+%22paragraph+number%22+&num=100&hl=en&lr=&rls=GGGL,GGGL:2005-09,GGGL:en&filter=0

Stevan Harnad