Jason Kottke notes the now-near universal practice of splitting newspaper & magazine articles online into multiple pages:
"...it's some sort of "best practice" that we readers let them get away with so they can boost pageviews and advertising revenue at the expense of user experience, but The New Yorker was the last bastion of good behavior on this issue and I loved them for it. This is a perfect example of an architecture of control in design and uninnovation."
It does ring true: I almost routinely now click on 'print-friendly version' when reading articles online, regardless of whether I'm going to be printing them, just so that I get an uninterrupted page without having to wait for a new set of ads and peripheral clutter to load at multiple interruption points while reading the article. It also makes it a lot easier to save a copy (single file) rather than having to save multiple pages. Surely the advantage of reading online is that the page layout need not follow print media's restrictions; so long as the article is mostly text it will be quick to download a long page.
Nevertheless, I can see that psychologically, an article which looks shorter may be glanced at by a casual reader - who may then become interested enough to continue - whereas one which looks longer may be ignored completely. This may be an additional explanation to the 'increase page views therefore advertising revenue' intention. I don't know.