We have had a great deal of success with our executives blogging in our internal Jive community. You can see a case study by The Community Roundtable that includes this: http://www.slideshare.net/rhappe/the-social-executive-ubm-case-study
If you're looking for more information, I'm happy to share it.
Ted and others,
How have you dealt with any concerns that executives might have had in saying the wrong thing, or having it construed in the wrong way and having it be discoverable in future? Any best practices to share when coaching your execs on these type of concerns?