Walking along the Palo Alto farmer's market with C3, my friend from Caltech.
Me: "Guess who was on the same flight as me two weeks ago? I'll give you ten yes-or-no questions."
C3: "Is it someone I know from Caltech?"
C3: "Is it someone in your graduating class?"
C3: "Ah, now I must be able to guess it, because there are fewer than 257 people in your graduating class."
C3: "This is going to yield less than one bit of information, but ... is it a guy?"
C3: "Oh! That was more than 1 bit of information."
(He didn't guess it in the end.)