(This is a comment that I made on Will Price's recent blog post http://willprice.blogspot.com/2008/04/lost-my-voice.html)
I would rather think that you should feel free to promote your company in your blog. What needs more caution is when you write about other topics, including what you learned from your management experiences.
In this age of personal broadcasting tools, people broadcast even what needs to be communicated silently between individuals. The world will eventually find new ethics, but right now people seem overshooting. It's not different here in Korea. A politician recently said, "Stop talking to a microphone. Let's meet."