Via CommLog, Michael Hyatt, CEO of Thomas Nelson Publishing, posts his company's Corporate Blogging Policy. The company encourages their employees to blog, and has provided a good set of guidelines, here's a snippet.
Be nice. Avoid attacking other individuals or companies. This includes fellow employees, authors, customers, vendors, competitors, or shareholders. You are welcome to disagree with the Company's leaders, provided your tone is respectful. If in doubt, we suggest that you "sleep on it" and then submit your entry to the Blog Oversight Committee (BOC) before posting it on your blog.
I like that Thomas Nelson allows for dissent amongst the ranks, provided it's respectful. It's important for a company to expect that every employee isn't going to agree with everything their employer says or does and encouraging thoughtful discussion, rather than ranting, seems like a smart move to me.
Another interesting note, the publisher also has a page that aggregates each employee blog post in real time, effectively creating an easy forum for fellow employees, and the company to follow who's writing what.