As a GM, I don't particularly like killing players. As a player, I don't like the idea that my PC could die in a random or meaningless way. When news about 4e was coming out, I found the rumored removal of save or die effects to be heartening. I know this upset many people, but I didn't really understand why - part of me chalked it up to sadistic DMs who were losing a favorite toy and whining about it. Jeff (who I know as a generally non-sadistic DM) tried to explain it to me, but I didn't really get his argument (particularly since he tends not to use a lot of save-or-die things in the games he's run that I've played in...).
Last night, Angela and I were talking about consequences for PC stupidity in her D&D game. She doesn't want to kill PCs outright - she'd rather teach them a lesson... but she feels like there aren't any system-supported consequences other than death.
Sure, there are roleplaying consequences. Neither of us mean to discount those. Part of the issue is that Angela's primary GMing background is in Wraith - a central conceit of which is that there are game-mechanical supports for roleplaying consequences. If you act on certain character flaws, you strengthen your Shadow and begin the descent to specterhood. In D&D, though, there aren't really game mechanics (at least not clear-cut ones) to support consequences other than injury, death, and theft.
I suppose that removing 'save or die' effects get rid of a major method of, ummm, imparting cosequences in D&D.
The thing is, I think that's a flimsy excuse that is used to cover deficiencies. There should be plenty of other consequences than death. If you're running a roleplaying-heavy game, PCs care about things and have beliefs. It is easy enough to violate them. Case in point: in Angela's game, there's a PC (a shaman of a death god who hates undead) who has been very careless. What if his carelessness resulted in the creation of some undead monstrosities. For roleplaying-light games, such things are trickier. Its there that I think some sort of game-mechanical support for consequences other than death is really needed (not that it isn't welcome in a roleplaying-heavy game). I think that this is one of the things that I really like about Spirit of the Century/FATE - you can stick negative aspects on PCs that follow naturally from their actions.