Characters in 4th Edition who are knocked to zero hit points wind up on "death's door". They are unconcious, and each turn on their action they can roll 1d20. On a 10 or less they slip closer to death; three such failed rolls, and they die. On the other hand, on a 20 they wake up and get back in the fight with the benefit of a healing surge. In the event that a player continues taking damage after going unconcious, they'll die when they hit their bloodied value in negative hit points.
This is a great system. It takes players on average six rounds to completely die, which is longer than your typical combat. Unconcious players have something meaningful to do on their turn with the possible reward of revival for a good roll. Healers have plenty of time to get their friends back on their feet. Really, a player should only ever die if the entire party wipes together, and in that scenario DMs have plenty of opportunity to have them all saved or thrown in prison instead, if that's your play style.
It's great because not playing isn't fun. If we wanted to not play, we could not buy the rulebooks and not turn up to sessions of the game. The difference between unconsciousness and sitting at home with a good book is a question only of degree.
The occasional couple of missed rounds interject some genuine threat into combat encounters but beyond that players are just being punished for playing heroic fantasy as though it were heroic fantasy. There are plenty of exciting games about never taking chances and only attacking when you have an overwhelming chance of success, but they are not Dungeons & Dragons.
So I found this on the ENWorld forums today:
"Well maybe I take game too seriously in this case, but I personally penalize death a lot. This means most of the time that the player will have to wait until the end of the *adventure* before re-joining the group and usually arrives with a character which is at least one level lower than the lowest level character in the party (I reward experience individually).While the dead waits for playing again, he can assist me as a DM in the adventure, interpreting NPCs or other situations."Oh sweet Jeebers. This is wrong on so many levels. First of all, how did your player die? Did the monsters keep attacking him after he was unconscious, instead of taking down the players who were still dealing damage? "Monsters Who Are Also Self-Defeating Jerks" is one of the lesser acknowledged dangers of dungeoneering.
Secondly, why are you punishing him for death? Are you saying he didn't avoid death to the best of his ability? Watch out for next game, when he'll stay back at the tavern rather than going dungeoneering. Are you saying he displayed inadequate skill in combat? This probably means he's a less experienced player; killing his character and getting him to sit out a session is not a great way to encourage him back for more games. Or was the guy just being an unrepentant idiot? Rather than dumping him for a session you might be better off talking about the issue directly.
Next, you're making him sit out a session AND getting him to roll up a new character? If losing his character wasn't a punishment to him you've got bigger issues with this group than death-happy adventurers, and players skipping a session isn't going to help them any. The only reason a character should ever permanently die is if it makes good story; if that's not what's happening here, your first and most important duty as DM is to find a clever way to save him. If resurrection cheapens death for you then don't let him die in the first place.
And last, your guy's coming back lower than the lowest-levelled player? So the punishment for being too weak to survive a combat is... getting weaker? That's what's called a "vicious circle". And again, that's on top of skipping a session and losing your character.
If this DM's players are really enjoying this type of play in full awareness of the existence of other options, then more power to them, they should keep doing what they're doing. But for everyone else out there, if you're playing like this, do the world a favour and stop.