A Different Kind of Quiz

About six months ago I was at a big conference. I was scheduled to present at 2 PM to an audience of 500 or 1,000 people. Another speaker was on from 1 to 2 PM. I told the organizer I would be back by 1:45 PM, leaving plenty of time before I had to hit the stage.

At 1:30 I got a frantic call to get back to the room as fast as possible as the prior speaker was going to finish 20 minutes early.

Why did the other speaker finish 20 minutes early?

First correct answer gets a signed book and (assuming a new batch actually gets made) a not-for-sale-in-stores Freakonomics T-shirt.

This is an impossibly difficult quiz, which means that it should take blog readers at least 45 minutes to get the right answer.

[[Update: The 76 guesses so far are all incorrect, although many are very clever. I told you this was a hard one.]]