"Bloggers learn lesson: Don't trash your boss" about a woman working in Iqaluit (the capital of Nunavut, one of Canada's territories in the north) as an agent for Nunavut Tourism. Seemingly benign comments were seen to be negative and she was dismissed without warning. Quoted from the article:
"The general rule is you can get fired if your off-duty conduct reflects badly on the employer," said Howard Levitt, lawyer and author of Law of Dismissal in Canada. "Her case is really close to the line."
Other rules of thumb: don't name names, and always assume your blog is publicly available, no matter how private you intend it to be. See these comments about a Toronto Starbucks employee who recently was dismissed for blog postings that were not so benign, courtesy of BlogCritics:
The original story: Employee fired by Starbucks over Blog
A rebuttal: Starbucks' blogging barista fired fairly.
Finally, Blogger has this article: How Not to Get Fired
Because of Your Blog.