Lots of people have blogged about how your business model affects your game design. Here's yet another way of looking at it. This may sound like a slam on 3rd Ed but it's not - all I'm doing is pointing out that the nature of D&D fundamentally changed with the release of 3rd Ed, and the business model made that happen.
3rd edition D&D was almost completely open source - so much so that Paizo has been able to effectively re-release it as Pathfinder. Of course, the people at Wizards of the Coast said, "If we make this free, so that everyone can download most of it off the internet, how are we going to make money?" Every way they could think of: selling books (effectively merchandise at this point, something you buy because it's more convenient than looking up the rules on the internet, or because you're in a store and it's there and tempting, or because it looks good on your coffee table) and add-ons (splats, modules) and miniatures.
And, of course, they wanted to encourage their players to buy these things. The problem, as I see it, lies with the modules and miniatures. Moldvay's edition of Basic D&D - I believe the most popular D&D product in terms of units sold - said, on the back of the box: "This is a game that helps you imagine." Miniatures weren't required. Even modules weren't required - you could get a whole evening of play by rolling up some encounters on random tables.
But now they want to sell pregenerated modules and miniatures - so they design a game that's heavily about tactical combat, about moving your playing pieces around on a board, so you'll be encouraged to buy miniatures. And they design a game that's complex enough, that takes enough time to block out encounters, that it's almost foolish to design your own adventures, or make up what happens on the basis of encounter tables, so you're encouraged to buy modules. In comes the railroad. Out goes the imagination - instead of imagining whatever we want, we're constrained by the minis and modules.
Obviously, a lot of people - probably even most people - like their D&D that way. The minis and modules bring a huge amount of clarity and rigor to the game, and make it a more consistent product. And while the old Red Box Basic D&D may have been the single most succesful D&D product, certainly much, much more money was made off of 3rd edition in all.
But it had now become a different game. A game I enjoyed some for what it was, but never got the same sort of awesome out of as I did with Basic D&D or Paranoia or Call of Cthulhu or Space Opera or the new school of indie rpgs like Apocalypse World - games where it's all about the imagination.
So - am I suggesting we avoid free-to-play? No, of course not, I'm planning on making sixty second shooter free-to-play. I'm just saying I'm going to tread carefully on the path and try not to lose my way.