CJ,
This is a great question and I am sure you will get a lot of varying answers. The first thing you really need to ask yourself is what your intension is with the blog. Are you looking to express your inner self? Are you wanting to attract more local business? Do you want to establish yourself as an industry pioneer or expert and move into writing and/or speaking?
Now the beauty of a blog is that you could really accomplish all that by creating categories specific to each aspiration. The downside is that it will take five times as much time to do all three rather than focusing on one specific goal. Also, if your goal is to place as an industry expert, your personal expressions in another category could shoot you in the foot. So you always have to think about what you say. That's not to say that you can't put personal expression into your writing even if the focus is on recognition.
Just remember, you can always delete it... but you can never take it back.
Now on my blog, I focus mostly on articles specific to my industry. this does two things for me: 1) It helps to establish myself as an expert so I can eventually move into writing and speaking, and 2) it increases my sites content relevance to my industry which will help with SE ranking.
I have a rather dry sense of humor and not everyone gets me when I put it in writing, so I tend to not blog 'from the cuff' so I don't risk offending someone that could become a client.
I don't know if that helps any or not. Hopefully it did.
Best of luck CJ.

