Looked at from a bird's eye view: Vizzini's death falls into the "just deserts" category. He's a difficult sort who could probably make Gandhi want to punch him in the nose (so very little emotional connection with the audience; they won't be disappointed to see him go), and he. He shows no concern for putting others at risk to further his own goalsgoals; he's not just reckless, he gleefully uses their danger to his advantage (again, the audience will be ok with his death - I certainly laughed).
A delightful summary of how this works in plays and movies is in "Rosencrantz and Guildenstern Are Dead". Guildernstern talks with an actor who unpacks drama's guiding tricks and principles (from within a play inside the play - cool trick that is pulled off without a hitch):
Player: Events must play themselves out to aesthetic, moral and logical conclusion.
Guildenstern: And what's that, in this case?
Player: It never varies — we aim at the point where everyone who is marked for death dies.
Guildenstern: Marked?
Player: Between "just desserts" and "tragic irony" we are given quite a large scope for our particular talent.