The downfall of many adventures has been the attempt by the writer to write a story in which the players could participate: this always leads to player reactivity and dissatisfaction. Ideally, the adventure writer (or module publisher) should produce a number of static adventure locales for the DM to stock his/her world with, and leave several clues in different places directing interested players to each. Few writers are willing to do this, however, and few publishing firms are willing to allow this, as it makes purchase of each new product very optional (whereas a series of sequels mandates purchase for full utilization of any one part).
Consider the example of module X10 (1985), which entailed a campaign-shaking all-out war, but left the exact alliances and outcome (and results afterward) entirely up to the DM and players' play. In the more recent revision to this excellent scenario by TSR, the entire campaign is planned out, yearly almanacs must be purchased to track the exact action, and forthcoming modules are dependent on the campaign alterations included within. This disease is also present in other games: namely the large-scale alteration (or construction) of a campaign site so as to set the stage for a particular series of modules. Perhaps first was the Dragonlance saga, which worked well, but in that case the modules came first, followed by more general interest in the campaign world. The circa-1988 revision of the "Gamma World" game is another example: a new campaign boxed set, followed by five linked adventures set there, followed by the death of the game. Or the circa-1986 revision of "Star Frontiers" which immediately killed that game system. Again, this kind of strong linking can be contrasted with EGG's nonlinear and tangential associations of the adventures in WG5, WG6, WG4, and S4.
Other examples are available everywhere. There is the Dark Suns setting by TSR, a fantasy boxed set launching a narrative in a series of modules. There is the progression of the campaign setting (and radical alteration) in the Battletech game. And, you have the "computer crash" staged in the Paranoia game setting, enabling a few new modules, and then the effective death of that system. Even the long-lived World Of Greyhawk setting perished by TSR's attempt to "breath new life" into it, where two boxed sets detailing massive changes to Oerth were followed by cancellation of the setting.
Again, the susceptibility of games to this disease is clear. To a publishing house, "breathe new life" into a game system means to sell more product, preferably the higher-priced campaign boxed sets. The strategy to this end is something like this: radically "update" or alter the campaign setting (and thereafter, all adventures and accessories), thus "mandating" that interested players purchase the update. The strategy, it seems, backfires: after the initial burst of product sold in the move, ultimately one loses total consumer base. Only some percentage of the previous gamers will purchase the new setting; those that decide not to are henceforth out of the game and won't be engaging in forthcoming product purchases. It seems highly unlikely that new customers will be attracted. And, in this narrowing of the customer base and interest (especially if the stratagem is played out multiple times, as with the World of Greyhawk "WARS" to "From the Ashes" boxed set devolution), the game becomes unsupportable and perishes. I predict (August 1994) that the same result will come from TSR's sudden turn to the long-established, and successful (if sometimes a backwater never suffering from a white-hot explosion of interest) D&D "Known World" setting, as they publish new "updates", "almanacs" and convert the setting to AD&D play.
Meanwhile, TSR's desperate attempts at luring new players/customers/RPG'ers into the D&D game (i.e., expansion of the consumer base) with such forays as introductory D&D boardgames, videotapes, and CD audio disc games, have certainly alienated old gamers in their constant philosophy of simpler, simpler, simpler (that is, more childish). I don't know if this strategy is working for TSR, but it certainly seems as though the RPG gaming base is finite and limited, and my gut instinct is that such advances are limited at best.