While addressing the question What Should Your Corporate Policy Be On Blogs?, Dave Pollard makes the point in strict opposition to what most other blogging gurus are advocating.
With rare exceptions, don't have an 'official' company blog: Most people are skeptical of anything they read on official company sites, and that will usually negate any value they might have in making your company appear more personable and responsive to customers. Blogs are personal and casual. Most business communications are not. Be cautious and talk to your marketing people before proceeding. Don't forget, blogs are a significant time commitment to maintain, and a blog that is not frequently updated or not well maintained is worse than not having one at all. If you do decide to have a company blog, make sure you know who its intended audience is and that this intended audience is the group who will actually be reading your blog. Blogs (like other corporate websites) are more likely to attract potential recruits, alumni, competitors, potential allies and the media than customers. If your actual and intended audiences are very different, you're wasting your time -- and your readers'.