According to a GlobeScan survey for the BBC-Reuters-Media Center “We Media” Forum, reported by Red Herring, "Bloggers rank lowest on the scale of trusted news sources".
Given that most blogs are essentially personal journals, this is no surprise. There is absolutely no reason why they should be trusted in the same way as conventional media, populated by professional journalists.
Bloggers usually offer openly subjective perspectives on the topics they cover. As long as readers are aware that blogs essentially offer personal opinions, they can attach as much, or as little, trust to the blogger’s views as they would to any individual’s views. I liken some bloggers to columnists in magazines or newspapers – they are essentially online writers who offer an opinion, but not necessarily the more balanced perspective demanded of professional journalists. Some views I will respect, others I will reject. But I certainly don’t regard them in the same way as major media organisations such as the BBC, the Guardian newspaper, trade magazines, etc.