Stormtower said:This. IMO, ideally the DM sets up difficult but not impossible challenges for players to overcome with their PCs. That's not to say a TPK can't happen, but the most recent two editions of D&D (3rd and 4th) spend a good deal of time addressing encounter balance, suggesting that PCs should be "winning" most encounters while occasionally being pushed to the edges of their abilities with truly deadly stuff.
Players loosing against a sound challenge (TPK or fleeing the dragon before saving the princess) is a kind of DM "win". The problem is that in D&D 3.x such thing can happen too often and in much anti-climatic way.
Hopefully, such situations are gonna be more dramatic in 4E with less save-or-die, action points, etc.