I've learned a bit about a Watson from internal IBM information and this is something they understand and are working on. There are serious ethical concerns about what to tell someone, even if the diagnosis is quite compelling, IOW, "you have 6 months to live" needs to come from a human. Obviously, the approach is to have it work as a tool for a doctor, not as a WebMD type self-diagnosis service. There are all kinds of follow-up questions, which you'd need to be a doctor to even answer, because they'd be couched in medical lingo e.g. systolic/diastolic blood pressure.