Moral Event Horizon: Quaid crosses it when he humiliates Abby and only goes farther from there.
In the short story, Quaid crosses it when his imprisonment and psychological torture of Cheryl leaves her mentally broken.
Squick: Cheryl eating the rotting, maggot-infested meat.
They Changed It, Now It Sucks!: There's some distinction that the change to the ending causes this. In the short story, Quaid, when confronted with his dread, succumbs and dies. In the film, he overcomes it and is basically on his way to becoming a Scarecrow-like villain. One could mourn the poetic ending, while others feel it created an awesome new horror character for movie sequels.
