Petty plot point pet peeve

[Smeghead]

For some reason, I recently seem to be repeatedly coming across examples in books where the Bad Guy has the Good Guy at his/her mercy and administers some sort of truth-telling drug/magic spell/polygraph machine type thingy that forces the Good Guy to answer questions truthfully. Meanwhile, the Good Guy is desperately trying to hide some vital piece of information from the Bad Guy. But luckily, through some chance circumstance, the Bad Guy doesn't ask quite the right question, or gets distracted, or offhandedly tells the Good Guy to shut up just in the nick of time, or whatnot, and the vital piece of information remains withheld.

So. To all Bad Guys with magical compulsory truth-telling technology: if you find yourself in this situation, here is the only question you'll ever need, guaranteed to extract the information you most badly want. Ready? Here goes:

"Tell me the one piece of information you are most desperate for me not to find out."

Simple, elegant, foolproof. If that piece of information turns out to be useless, like "I used to masturbate to a Sears catalogue when I was 12", then move on to "Tell me the one piece of information you are NEXT most desperate for me not to find out."

Let's put an end to this particular example of lazy writing.

[Enderw24]

"Tell me the one piece of information you are most desperate for me not to find out."

BOND: I just slept with your wife.

[Snooooopy]

Hours later, the bad guy has nothing actionable, but has learned all the things the good guy likes masturbating to. "Tell me the one piece of information you are most desperate for me not to find out that doesn't involve one of your surprisingly degenerate personal habits" may cut out some of the useless stuff.

[The Other Waldo Pepper]

"Tell me the one piece of information you are most desperate for me not to find out."

Simple, elegant, foolproof.

"First I'm gonna use you as human shield, den I'm gonna kill dis guard over here with da Patterson trocar on da table. And den I was thinking about breaking your neck..."

[blindboyard]

Hours later, the bad guy has nothing actionable, but has learned all the things the good guy likes masturbating to. "Tell me the one piece of information you are most desperate for me not to find out that doesn't involve one of your surprisingly degenerate personal habits" may cut out some of the useless stuff.

Won't work. The intelligence services will just have their operatives masturbate to top secret information. Nuclear weapons plans will be printed on pictures of explicit sex acts.

MY favourite example of this trope:

GROFF There is a member of your crew we cannot find. Orac. Where is he?
CALIPH The neuronic whip is on an automatic setting. It has only to sense one lie and it will boil your brains in your skull. Where is Orac?
TARRANT If he's not on the ship, I don't know where he is.
CALIPH How tall is he?
TARRANT About so high. (Tarrant demonstrates)
CALIPH A dwarf?
TARRANT We never think of him as one.
CALIPH What is the color of his hair?
TARRANT He hasn't got any.
CALIPH He's bald?
TARRANT A bald dwarf shouldn't be too hard to find.