[lmkg]

Part of 'the "Toronto" problem' is simply the format of the challenge. In Jeopardy, Watson can give at most one response, in that particular situation exactly one. In a medical diagnosis situation, Watson's responses wouldn't be so constrained. He could give a list of 20 possibilities, with confidence margins for each one, and even as far as a list of possible additional tests designed to favor one possible diagnosis over another. This sort of information, utilized by a competent doctor, has a far, far smaller potential for disaster than the "what is a lobotomy?" scenarios that people are scared of.