Earlier quoted context omitted.
It's more than a search engine it aggregates the information from say 10 different studies or cases about a disease into a set of information which it then compares against the current case the doctor is looking at. At that point it posits some diagnoses or some treatments. Calling it a search engine is pretty dismissive.
I agree, this is a lot more than a search engine. But I guess that over time it will have to deal with the same issues that search engines do. Think drug company or test procedure journal spam, designed to SEO Watson into making specific decisions or recommendations.
Ideally if Watson were able to parse documents well enough they would have to actively lie in order to twist Watson that way. Also a lot of what goes into Watson is peer reviewed in the medical field iirc so there's also that buffer.