It was all Watson in Day 2 of the Jeopardy IBM Challenge, until Final Jeopardy anyway. The category was "U.S. Cities" and the clue was: "Its largest airport is named for a World War II hero; its second largest for a World War II battle."
The human competitors Ken Jennings and Brad Rutter both answered correctly with "Chicago" but IBM's supercomputer Watson said "Toronto."
Watson was mocked on Twitter for the mistake, as of course Toronto is a Canadian city. Wrote one Tweeter, @writersblanc, "Oh Watson... 'What is Toronto?' Why not ask 'Who is Arcade Fire?'" Said another, @erickohn, "Watson guessed 'Toronto.' Toronto! The machines don't know all. Yet."
Fortunately, the super-machine didn't wager much and he still won big, finishing with $35,734 to Rutter's $10,400 and Jennings' $4,800.
UPDATE: IBM posted this explanation for the mistake on its "Smarter Planet" blog:
David Ferrucci, the manager of the Watson project at IBM Research, explained during a viewing of the show on Monday morning that several of things probably confused Watson. First, the category names on Jeopardy! are tricky. The answers often do not exactly fit the category. Watson, in his training phase, learned that categories only weakly suggest the kind of answer that is expected, and, therefore, the machine downgrades their significance. The way the language was parsed provided an advantage for the humans and a disadvantage for Watson, as well. "What US city" wasn't in the question. If it had been, Watson would have given US cities much more weight as it searched for the answer. Adding to the confusion for Watson, there are cities named Toronto in the United States and the Toronto in Canada has an American League baseball team. It probably picked up those facts from the written material it has digested. Also, the machine didn't find much evidence to connect either city's airport to World War II. (Chicago was a very close second on Watson's list of possible answers.) So this is just one of those situations that's a snap for a reasonably knowledgeable human but a true brain teaser for the machine.
Scroll down for video of Watson's Final Jeopardy blunder. And catch up on Day 1 of the competition here.