Information Hub Blogs (unfortunately behind a pay wall) is a relatively old paper by my own prof, Judit Bar-Ilan. The paper content-analyses a set of 15 professional blogs in computer, library and information science. What's especially good about this paper is that is has an excellent literature review about the definition of blogs and the categories they can be classified into (by authorship, content, style...).
The conclusion is that these blogs act as filters and concentrate relevant information ("one stop information kiosks or information hubs"). These blogs are meant to disseminate professional information, as opposed to personal blogs, and rarely deal with the author's private life.