I hear this question from friends and colleagues in B2B Marcom (business to business marketing communications). It's a good one.
According to The Content Factor website , "The Content Factor has developed To Blog or Not to Blog, a white paper that provides the basics - and more - on corporate blogging." On the same webpage, Doc Searls is quoted as having said, "To Blog or Not to Blog provides a well-written and well-sourced guidance for companies that haven't yet come to grips with blogging - but need to." That's good enough for me.
Another interesting perspective appears just below this post in my Stowe Boyd interview.