The omnipresent casual/hardcore ideology has lead to those who think that death should be trivial and happen rarely, and those that think that death should happen all the time and be harsh.
Both is wrong. While the 'casual' point of view at least works in arcade games, the 'hardcore' point of view only works in the most niche and most gamey games.
To those who claim to care about the simulation and often lean towards the hardcore side, I say: Death is not immersive. Whenever your character dies you are violently thrown out of the simulation. Great games instill a desperate fear of death in the player without having him die all that often - never if possible.
To those who think that frequent death is a necessary gameplay element, I say: Death should not be abused for gameplay purposes. There are better ways to give the player clear feedback about is actions.