Death, that horrible finality, is what makes life. It is the ultimate ending, the last word, the balancer that brings completion to every existence. Without the closing that death brings, life itself would have no meaning. It is defined by the very mortality that we strive to overcome. But certain games don't necessarily need to include death amongst their list of options. After all, if you're playing a video game and you die, what is the penalty? You must restart from the last save or, if the game is old enough or hard enough, play from the very beginning. The first is a false penalty that only serves to eat up time. The second is a penalty that stresses completion and skill as important factors in gameplay. Both are slowly falling by the wayside in modern game design.
There is a line of theory, and a good line it is too, that says that since dying in modern games is generally just a minor irritant, there's no reason to even include it in the game. It is a false penalty, one that wastes time but fails to have any real impact on the player other than forcing them to replay things they have already done. This issue was brought to the forefront for me by the excellent game Braid in which the player actually cannot die. And for video games, this is perhaps a valid argument. It certainly played out well for Braid.
We can compare this to some computer roleplaying games (or at least games that bear that title). For example, Baldur's Gate relies on thrusting you back onto old saves to replay areas that you failed at. I'm not saying this is necessarily a bad thing, especially in Baldur's Gate where the autosaves were sparse. This system is much more similar to the old-style Nintendo and Atari games where a supply of lives is drained until you have to start over. Another modern(ish) computer RPG that we can look at is World of Warcraft. The system that follows death there is a slap on the wrist; you may come back to life instantly with the only real penalty being a brief cooldown period where your core statistics are reduced, the loss of some money (through damaged goods), and the irritation of having to walk back to where you were.
While it is debatable whether or not World of Warcraft and Baldur's Gate are actually role-playing games, they have had an undeniable affect on the game industry. As part of the PC bill of rights that I discussed earlier in the Delicate Balance, player's have grown used to the 'right' that says they cannot die unless they want to or unless they are incredibly stupid. Unfortunately, that plays right into the issue. It may protect players from abusive DMs—I'm not denying that they exist—but it leads to a no-consequence game.
Death in a pen and paper roleplaying game is an extremely important factor. It is an engine of change, the only real threat that matters. I've heard a lot of players complain that losing their equipment or their manor-houses, or whatever other perks they've accumulated is just as potent as losing their characters. That is clearly false, and we can point out the falsity of that statement simply: Death of a character is permanent. Removing equipment is temporary. Character-death is at the heart of D&D; it is not a storytelling game (hey, I like storytelling games! I play a lot of 7th Sea! That's not what D&D is about). If you want to play a storytelling game with D&D I can't stop you, but it's not what the rules were intended for.
Death allows change. In a world were characters can't die, there is stagnation. Life is movement! Life is survival! In a world where you cannot die, you also cannot survive. To remove the teeth of death is to disenfranchise the player completely. You aren't helping your players by making sure they don't die. Players, you aren't winning when you win that 'right.' You are removing an integral element of the game that makes it no longer a game but a story. Maybe that's what you want! But if it isn't, think about it before you get angry.