Good articles, Yellowwing.
They point out exactly why large corporations need to be careful in what they say in their blogs and have to make sure their employees understand what's off limits. In that respect, blogs are like any kind of public statement, be it a message board, or an interview with the press, etc.
Small businesses and freelancers, on the other hand, can generally be more open. They have fewer constituents to tick off, fewer secrets to worry about revealing, and they are not examined as closely as large corporations for every small thing they mention.
That's why I think blogs can be much more spontaneous when used by small businesses, but will be more restricted when used by large corporations.