IBM is now encouraging their 300k+ employees to blog if they want and has posted a policy to set their expectations for employees who do blog:

Guidelines for IBM Bloggers: Executive Summary

• Know and follow IBM’s Business Conduct Guidelines.
• Blogs, wikis and other forms of online discourse are individual interactions, not corporate communications. IBMers are personally responsible for their posts. Be mindful that what you write will be public for a long time — protect your privacy.
• Identify yourself — name and, when relevant, role at IBM — when you blog about IBM or IBM-related matters. And write in the first person. You must make it clear that you are speaking for yourself and not on behalf of IBM.
• If you publish a blog or post to a blog and it has something to do with work you do or subjects associated with IBM, use a disclaimer such as this: “The postings on this site are my own and don’t necessarily represent IBM’s positions, strategies or opinions.”
• Respect copyright, fair use and financial disclosure laws.
• Don’t provide IBM’s or another’s confidential or other proprietary information.
• Don’t cite or reference clients, partners or suppliers without their approval.
• Respect your audience. Don’t use ethnic slurs, personal insults, obscenity, etc., and show proper consideration for others’ privacy and for topics that may be considered objectionable or inflammatory — such as politics and religion.
• Find out who else is blogging on the topic, and cite them.
• Don’t pick fights, be the first to correct your own mistakes, and don’t alter previous posts without indicating that you have done so.
• Try to add value. Provide worthwhile information and perspective.