Just because Wikipedia is wonderful (well, mostly) doesn't mean that there's no room for other wikis serving narrower domains. For example, one of the quips that is frequently made as a criticism of the crowd-sourced Wikipedia way is that you wouldn't want the same approach in the operating theatre. Well, maybe not, but this shows how you can usefully apply wikis to medicine:
The Medpedia Project is an extraordinary global effort to collect, organize and make understandable, the world’s best information about health, medicine and the body and make it freely available on the website Medpedia.com. Physicians, health organizations, medical schools, hospitals, health professionals, and dedicated individuals are coming together to build the most comprehensive medical resource in the world that will benefit millions of people every year.
In association with Harvard Medical School, Stanford School of Medicine, Berkeley School of Public Health, University of Michigan Medical School and other leading global health organizations, the Medpedia community seeks to create the most comprehensive and collaborative medical resource in the world. Medpedia will serve as a catalog, database, and learning tool about health, medicine and the body for doctors, scientists, policymakers, students and citizens that will improve medical literacy worldwide.
The key thing here, of course, is that only people who know what they are talking about will be allowed to add content, making it closer to the Citizendium model than Wikipedia (although the latter continues its slow waltz in that general direction too.)
Let's hope that other knowledge domains pick up on the idea: you simply can't have enough of this open content (Medpedia is under the GFDL, like Wikipedia).