AbdulAlhazred
Legend
Those DMs would also be missing the fact that 'saying yes' to the player who wants his character to swing 50 feet across a room, on a chandelier, and then attack his opponent at the end of it can also be quite educational for that player, when his character goes splat, prone in front of that enemy, who then whacks him with CA.
Saying yes doesn't imply that the player ultimately gets his way.
Right. The 'yes' was firmly in the vein of "Yes, I'll allow you to try to do that. It may be ill-advised and the DC may be preposterously high, but go ahead." as being a perfectly legitimate response in some cases. Note too that the section on skill challenges discusses the narrative requirements for a player action as well. The overall advice is to let players try things, but the things they attempt still have to have narrative justification and may or may not produce the results desired.
"Say yes" certainly does also plainly aim at narrative/plot/setting input by the players. This is discussed in more depth in DMG2 (which has probably the best discussion of this topic in print anywhere). Several good examples are given. This kind of thing should be a significant tool in any good DM's toolkit. Notice also that DMG2 revisits the more specific 'say yes' advice, where it provides some more depth and notes that saying yes is indeed not a license for players to trample all over the DM (stated more in the line of 'yes... but ...' ).
I think 4e is pretty consistent in this regard and the advise they give is quite cogent. I'd say there are MANY DMs out there who might improve their games if they took it to heart. I know I've gone more out of my way in this regard in the last few years and it always seems to work well. I can imagine some players who might be unfit to wield such responsibility, but then if the DM is weak enough to be pushed around by those players there's more going wrong than a bit of advise is going to fix.