Now, just mulling over this a bit more. Under the d20 rules as we know them, a number of factors can contribute to a character's death: the player may have made a mistake, another player might have made a mistake, the DM might have over-estimated the difficulty of an encounter, or the dice might have been against the character. The upshot of it is, sometimes a character dies when nobody at the table wants him to die, or thinks that it is a good thing that he died. Some gamers consider this to be a problem, not a feature.
In D&D, the historic solution has been spells like raise dead and resurrection. If the DM didn't want you to die in any edition of the game, some NPC cleric would come along and cast the necessary spell. Of course, some gamers consider this an inelegant fix.
There have been other proposed solutions to the death problem, and these tend to take the form of safety nets, e.g. the character is unconscious instead of dead by expending action points/hero points/fate points, or to place the decision in the hands of the player. In other words, the character risks death when the player thinks that the in-game objective is worth it, e.g. "death flag" rules.
I personally am not too keen on death flag rules, but I would prefer some kind of safety net over the current approach of raise dead/resurrection.