Scientific Blogging

I'm quite often wondering what it may mean the be a "scientific" or "academic blogger". Does it include to write about an review papers? Could many scientific bloggers replace or at least complement the traditional peer review system? Never arrived at a real conclusion - but came accross this site: http://www.postgenomic.com/ today. It is a portal site to life science blogs. With "most talked about academic papers", an online impact tracker for journals and more .. very nice.