1. Know and follow IBM’s Business Conduct Guidelines.
2. 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.
3. 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.
4. 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‘spositions, strategies or opinions.”
5. Respect copyright, fair use and financial disclosure laws.
6. Don’t provide IBM‘sor another‘sconfidential or other proprietary information.
7. Don’t cite or reference clients, partners or suppliers without their approval.
8. 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.
9. Find out who else is blogging on the topic, and cite them.
10. 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.
11. Try to add value. Provide worthwhile information and perspective.

—Guidelines for IBM Bloggers: Executive Summary (IBM)

A good set of guidelines for the blogosphere in general.