I also travel to Bali a lot, and on one of my trips last year I was traveling with a friend who had NO more regular full pages (as the other poster mentioned, you need an entire page). He only had the final back pages that are reserved for Amendments and Endorsements. The immigration official at DPS flipped through every page of his passport, and finally pointed out that he had no more entry/visa/departure pages. My friend was caught totally unaware, and then simply asked the immigration official to stamp one of the empty back pages. The immigration official then tried to get my friend to give him a bribe, to which my friend suggested that maybe the immigration official needed to bring over his boss to see if the back page could be stamped. After that, the immigration official simply shrugged and let him get the visa on one of the back pages.
So, while I don't suggest having no free pages, I have to wonder if the original article you read might have been a misprint. Maybe it should have stated that you need 6 open spots- four for the full page Visa sticker and then two spots for the entry and exit stamps. Though... every one of my Indonesian entry and departure stamps has been done right on top of the Visa sticker. So, I simply cannot see why you really need more than one full official entry/visa/departure page.
