I use several blogs, as a notebook, as a way to show and tell my friends and family what I have seen, as a private, invisible Hyde Park, as a place to put book reviews and publicize my own book. A blog is a place where writers can chat, quickly, off-the-cuff, and without revision. There is little sweat involved, no blood and rarely tears--all of which are prodigally spent when a book is written.
This new enticement to people who blog makes a vanity press look good. At least finished manuscripts are submitted in varying degrees of competency to those who are paid to publish them--not a rapid outpouring of quick thoughts on a multiplicity of subjects served up in a few words.
I know there are books--and good books--that have been born from a blog, and that many good writers use blogs as a tool. I also know that before those books go out into the world, they have been written and rewritten and shaped and burnished and torn apart and put back together. This is what writers do--this is what writing is. Blogs are a valuable five-finger exercise but they in their raw form do not make a manuscript, and anyone who implies that they might should be locked in a room with only bound and printed blog posts to read for the rest of his or her natural life.