When I first started blogging, it was sort of half business and half personal. I had another site and wanted to keep in touch with my members. Then when the site didn't work out, I was posting my own things in my blog and it became personal. Now that I accept sponsored posts, looks a bit like a business blog again. Really funny how things turn out in the end. But I agree with what has been said so far. Personal blog for doing your thing and business blog for serious stuff like reviews, tutorials,
SEO tips, layout/themes, etc. And yes, someone mentioned niche blogs. I guess those are ones that you can have a bit of personal and business "voice" too depending on the topic.