There has been a bit of chatter about the Tyranny of Fun[1. I picked that post because it excerpts the core bits of Melan's larger post at the RPGsite, which you can read here: The Tyranny of Fun: status report.] that has come to dominate the design of D&D. I have some sympathy for those on both sides of the argument. Chatty points out that it injects more incendiary material into the edition wars. I agree that demonising fun is stupid.
On the other hand, I do see a problem with thinking of fun as most important (it creates an false dichotomy between fun and whatever is supposedly sacrificed in its name), and I do think that because 4e tries to make everyone awesome[1. RPGpundit has more in The Tyranny of Fun pt. 2.] it ends up making awesomeness meaningless.
However, I think that the people arguing that a Tyranny of Fun exists are missing the real crux of this issue.
A commenter on a Paizo forums thread about Gygaxian Naturalism said this:
3e rejected a lot of Gygaxian crap, and boy am I glad it did. Some people might like the idea that a 2nd level party might wander into an ancient red dragon's lair, but I wouldn't want to waste my valuable gaming time with such stupidity.[1. pres man, Sun, Oct 5, 2008, 11:41 AM, in 4e's Rejection of Gygaxian Naturalism]
What makes me cringe when I read that is the idea that our time is so scarce and precious that we cannot afford to make any mistakes on the way to Maximum Fun. This idea is of a particular structure that, in leisure pursuits or love, promotes a race to the bottom.
The unfortunate reality is that safe, guaranteed fun does not exist. Seeking it leads to the rejection of anything that might be only perceived as a threat to that guarantee, regardless of the actual value of a new idea. The irony is that we, as humans, are not maximally entertained by the predictable and the routine, so standardising and formalising the elements that make play fun encourages finding a lowest common denominator. Seeking Maximum Fun forces us to aim squarely at mediocrity.
How does this relate to Gygaxian Naturalism in that quote above? Much of the success of D&D is that you can do anything. You can do anything in one sense, in that the DM can theoretically allow anything to happen; but the real impact of that feature of roleplaying games is that you can try to do anything, and see what happens. If you can't choose to walk blindly into that ancient red wyrm's lair at second level, there are hundreds of other things that you can't choose either that might end up being fun in ways that nobody at the table could have predicted. Constraining action to only what will predictably result in fun tears the entire foundation of D&D's fun out of the game.
It's not a Tyranny of Fun, really. It's a Fear of Unfun.