Medical blogs often complement journal articles. Even the popular medical portal Medscape prominently features the best of the medical blogosphere on its front page.
The Medscape founder himself says that "a variant of Wikipedia for medicine is the future -- and it's good."
User-created content has the power to expand and correct peer-reviewed content. Then, you need Google Medicine to find what you are looking for in this enormous mash-up of blogs/wikis/journals/books/sites that we call Web 2.0.
"Google, M.D." is not going to replace doctors but it will certainly help both physicians and patients to take care of each other.
It is nice to see that Medscape editors' opinion on medical blogs has evolved. As Nick Genes, the founder of Grand Rounds says, it only speaks of the quality of writing on medical blogs.
Wikipedia is based on the "Wisdom of Crowds" theory which claims that we all, together, know more than the best individual scholar. This may not apply to medicine though. Even Jimmy Wales, the Wikipedia founder says that "you would not like your brain surgeon to look up medical facts in Wikipedia".
Greg Linden of Findory talks about "Madness of the Crowds: Take a majority vote from people who don't know the answer, and you're not going to get the right answer. Summing collective ignorance isn't going to create wisdom."
Peer-reviwed literature is not going to be replaced by individual blogs. The Web 2.0 phenomenon is very new and we still have not figured out what is the best way to use it in medicine.
The idea of "open content" is great but what if the content itself is not that great?
Who Cares About Medical Blogs? The Video Answer of a Medical Media Company
Are Traditional Peer-Reviewed Medical Articles Obsolete?. Medscape
BMJ: Build Google Medicine
Is a medical Wikipedia a good idea? Respectful Insolence.
Can Wikipedia conquer expertise? The New Yorker.