Credible Bloggers?

In class today we talked and discussed quite a bit about bloggers and if we find them to be credible news sources. Most people did not think that they were because blogs are mostly opinion based. I personally do not know how to feel about this. I keep a blog myself, and yes, it is completely opinion based. I base my arguments on articles (which I link to) I have read giving my readers my opinion. I am not saying that I would consider my blog a credible source, because it is not, but there are some blogs I would consider to be credible. If you go to any news website, I guarantee you will find blogs by the news anchors or journalists who work for that particular news outlet. These are the types of blogs I would consider to be reliable news sources. I say this because first off, reporting the news are these peoples' jobs so I would HOPE I could trust them. Also, I would consider them credible because I feel like you can gain so much more from the blog. On their blog they have free range of what they can say which gives them the opportunity to elaborate on a story or provide details, which were cut from the story accepted by the editors. Because of this, I do not think we can just lump all blogs together and say none are credible news sources. There are quite a few that really are credible. Even though the opinion of the one writing will show through, how is this any different than the bias that can be seen on any news program?