Nobody could have foreseen this
Albeit for very large values of 'nobody'. In 2006 I wrote the following, with regards to John Ramsden's Don’t Mention the War: The British and the Germans since 1890:
[...] what’s with having the endnotes not in the book itself but on a website? Do they think websites are permanent? Will the 10 pages omitted from the book really improve its profitability by that much? It’s better than none at all, I suppose, but it does potentially diminish the book’s useability for research purposes, now and in the future. For shame, Little, Brown, for shame.
And of course, four years later the website no longer exists; the domain name is not even registered any more. It doesn't help that Ramsden died last year, so there's probably nobody looking after his electronic-academic legacy.
Luckily this is a trend which hasn't taken off -- at least not that I've noticed in recent book purchases. But Guy Walters at the Daily Telegraphdisagrees (citing Ramsden's website too, which floored me since his post seems to have gone up this very day!) He thinks that the practice of moving footnotes, endnotes and bibliographies from books to the web is becoming more common. I do hope he's wrong.