I was looking through my collection of Dragon magazines the other day, which dates back to the mid 80s, and remembering how many back issues of the mag we used to sell. Customers years ago used to come and browse through the boxes, seaching for a particular back ussue, much like comic collectors used to do.
Much of the searching from back issues by comic collectors came to an end with the advent of eBay, which made almost every issue a collector could want available for a price. The hunt for Dragon back issues came to an end several years before the widespread acceptance of eBay, when TSR released the Dragon Magazine CD-ROM, selling at the time for about $25 and now going for over $100 on Amazon. The CD held the first 250 issues of Dragon in a searchable format, so collectors didn't have to worry about searching down that elusive back issue any more. Less than a year after the release of the CD-ROM, our sales of Dragon back issues had tapered off to one or two a month, then nothing. We have gone months and even a year or better without selling anything from the Dragon backstock.
In a way, I think the Dragon CD helped usher in the era of the PDF game and online magazine. The people who bought the Dragon CD long before the rise of the PDF proved to companies that there was a market for the release of printed material in this format and that people were willing to pay for it, albeit a lower price, but they would pay just the same. Players got accustomed to reading the magazines on their computer, so it was just a short step to offering them other materials in electronic format.