In the April 7, 08 Businessweek: Busting a Rogue Blogger. About a person blogging anonymously on the 'Troll Tracker' blog, which followed patent trolls, and who turned out to be a Cisco patent attorney. As someone who has blogged both in and outside of a large company for years, this provided some useful insight into the dilemmas of separating the origins of opinions effectively. I had never read the 'troll trackers' blog, but the article says it was opinionated but largely innocuous.
Then there is always the problem of comments. Commenters' opinions can be much more volatile than the bloggers own. Bloggers love comments, because it is proof of engagement with their audience. So there is a tendency to allow more license to commenters than might have given yourself, to indicate your openness to other opinions. It was unclear how closely the comments were moderated. In this case comments included charges of acts that were felonies and even an implied death threat.
This case has ended up in defamation lawsuits against the blogger and Cisco. Including Cisco in the lawsuit shows how relatively little the 'my opinions are my own' disclaimer in blogs like this one mean. Also though Cisco was not involved in their employee's blogging, they do have an official public blog, where they recently included a post that updated their employee blogging policy, worth a read.