What people are saying is that there are ways to mitigate SoD, including PCs being prepared for the eventuality (either because they know there's a bodak in the dungeon, or because they have heard tell bodaks sometimes inhabit dungeons). The only one that is suggesting that SoD can only occur if the DM has completely briefed the players beforehand is you.
Except that when examples are given of a DM using a SoD encounter, the response seems to have been, "He was a bad DM for not briefing the players beforehand."
I dunno. Maybe I am just misreading a lot of opinions here. If so, my apologies all around. But it definitely feels like some of the comments have been saying that if someone dies to a SoD, it is their fault - or their DMs, for not giving them a heads-up.
It's D&D. Unless a house rule or group decision says otherwise, it can be assumed there will be SoD attacks -- poisons, death gazes and everything in between. Players that for some reason refuse to acknowledge the possibility may find themselves quite put out when they lose a beloved character for want of a relatively cheap and easy protection like anti-toxin or potions of death ward.
As I said, I can understand that style of play.
At the same time, I don't think that is a universally desired experience. I'm playing a mid-level character. If I don't have the system mastery to know that I need Potions of Death Ward, or my character doesn't have the money to invest in them, then its my own fault when I get taken down by a SoD effect?
And of course, part of the problem is that even taking precautions doesn't guarantee safety. If I get into a fight with a wizard, I might not know he has Finger of Death until he uses it. Or even if I see it coming - what if he wins initiative before I can drink my potion?
If I really want to be safe, I need even better protections, which means both greater system mastery on behalf of the player, along with more resources invested in these optimized items instead of more in-character pursuits. Now, a game focused on that type of challenge and competition can be fun, certainly.
But for others, it leads to more of a 'DM vs PC arms race' that many gamers are not interested in. Now, there is certainly a wide range of playstyles before it actually reaches that point, and not every game that rewards prepared PCs reaches that level or anywhere close to it!
But the presence of SoD - at least in my experience - definitely can push a group more towards it. Without it, if I walk into an encounter unprepared, and things start to go badly - I can generally cut and run, having learned my lesson, and come back later ready for the fight. When I run into SoD, instead, I don't have that option. Thus, encouragement to really build up system mastery and tricked-out PCs if I don't want to risk the loss of my beloved character.