WashingtonPost.com: Marketing Moves to the Blogosphere:

The strategy part is important because a blog may not work for every business. Before starting one, companies have to “make sure that the blog fits in with the existing culture of the company,” said Walter J. Carl, a professor of communications at Northeastern University who has studied corporate blogging. He says a blog is a “really bad idea” for companies that are secretive or tend toward non-disclosure.