Certainly, it’s rarely “when the player decides” (at least as far as D&D goes), but – likewise – we DMs are very careful to not arbitrarily killing PCs. At least if we want players to return to our tables. (Seriously: if you’re a player whose DM keeps killing your PCs for no good reason you can discern, leave the group and find a better DM).
The ideal death is one with meaning (preferably one that is a self-sacrifice). Having a death that relies on one die roll is not great, but if that one die roll was based on a chain of poor decisions on the part of the player… ah, that’s a different matter!
If the PCs waltz past the “danger, beholders ahead” sign, bicker amongst themselves, and get in each other’s way instead of working together (as they may have planned…) then, when one of the PCs gets disintegrated, everyone can look at each other and say “Oh, that was our mistake”.
It’s the “Players walk down a corridor on the first level of the dungeon, and a disintegration beam hits them” that we object to – and rightly so.
The original edition of D&D had a lot of death traps and cursed items. Cloak of Poisonousness is one of my “favourites” of that type. To identify it, you need to wear it. When you wear it, you immediately die of poison, no saving throw allowed. I saw writers trying to give “fair” ways of using the cloak, such as putting it on a creepy-looking statue or suchlike, but that’s not the entire story.
The playstyle of the group is paramount; especially if Wish spells and Raise Dead spells are common, then the Cloak just becomes another obstacle – it’s not actually a perma-death item, it’s just something to provide a warning of the dangers to come. When you’re not playing in that manner, though, the Cloak is out-of-place.
We’re shortly going to see a lot of players going through Tomb of Horrors for the first time (I know that some of my DMs are extremely eager to run it, probably because they’re sick of seeing their monsters being slaughtered by the adventurers). It’s important to remember that Tomb of Horrors was written in a different age, in which the Cloak of Poisonousness wasn’t so out-of-place. Also: Gary Gygax’s two best players were both able to defeat the Tomb because they were well-versed in the inventive dungeon-crawling style of the early D&D. Players today may be experienced, but not in the same manner.
So, when you’re getting ready to run Tomb of Horrors, make sure it’s what your players actually want to play – and not something that will lose you friends.