Blogs and peer-reviewed journals

For the last couple of months I have been searching the internet for good (and bad) examples of social web media used to communicate Public Health research. And although Public Health is not the dominating topic on scholarly web 2.0 communication the variety is still great. Putting the magnifying glass on blogs it becomes clear that scholarly blogs really do come in all shapes and sizes.
Among the many different kinds of blogs, it has been interesting to see how some of the traditional peer-reviewed journals now also offer blog platforms. BMJ is one of the high-impact journals that have an elaborate blog platform. With a total of 18 blogs in categories  ranging from “Disease in Childhood” over “Tobacco control” to “Medical Ethics” several public health topics are covered. The activity level on the 18 blogs differs. For some the post frequency is higher than for others and the extend of comments varies too. Also the objective of the blogs are different, ranging from providing a platform for discussion to highlighting articles from other journals (e. the Heart Journal Scan wich recommends cardiology related articles from non-cardiology journals). The blogs come with the function of regular blogs such as comments and posting it on twitter, facebook etc.
Other peer-reviewed journals also have blogs under their domain. This includes Nature, and PLoS who has both an official PLoS blog and PLoS blog network with more issue specific blogs. Eg. the staff of PLoS has a blog  and individual researchers have blogs related to their field.
Reading these blogs it makes me wonder what the reflection behind initiating them have been. What were the concerns and perceived benefits? How is the blog thought to relate to the “mother” peer-reviewed journal? Why does BMJ have a blog, but not the Lancet? Does the concept of the blog interfere with the fundamentals of the peer-reviewed approach? The questions are many.
Yesterday a friend of mine, and researcher herself said that she didn’t really give much for social media in research communication. But when I mentioned blogs of journals like Nature her response was  “It is funny, I do not really consider blogs as social media”. Perhaps blogs associated to journals washes out mentally some of the objections people have towards the combination of research and blogs. Perhaps the possibility of commenting is taken more and more for granted? I do not know the reasons, but it would be interesting to find out more about this…