There isn't too much "Web 2.0" tech behind building something Watson. Perhaps the use of ontologies and semantic web datasets, but in academic circles at least that's informally referred to "web 3.0" (that, too, is a bit of a misnomer because Cycorp has been building semantic ontologies for a long, long time).

Doctors virtually all use lightweight iphone or webapps (e.g. Epocrates) to handle drug information, etc. Like the rest of the world, they no longer memorize massive sets of evolving information, they simply walk around with their Iphone/device of choice and look it up.

The providers of such software now and in the future will of course employ teams of lawyers to craft appropriate statements like, "use this as a guide only and not as the basis for a diagnosis or prescription," which of course won't prevent doctors from using it as the basis, but it will keep a healthy sense of legal limbo which exists in many other fields.

Basically, I think this doesn't remove the doctor as the interface person, but it allows fewer doctors to see more patients and to streamline the process for many medical problems with (presumably) better outcomes on average. I'm usually not keen on the impersonal nature of modern medicine but what works, works.

Clinical decision support systems don't really create any additional legal liability. They just present the user with possibilities. The physician is still legally responsible for making a diagnosis, prescribing a course of treatment, and carrying out medical procedures.