Whenever I am talking to organisations about micro-blogging, I show them the Zappos example on Twitter.
See what online shoe retailer Zappos staff are doing right now.

I think this is brave and also a good idea as customers and people who interact with your organisation get an idea of what kind of people work there.
There are organisations that like this idea but they’d rather setup their own server and host their employees on them. Laconica is an open source microblogging platform. Companies can download Laconica code and install into their own servers and create their own private or even public microblogging networks. Evan Prodromou, the founder of Laconica says
Deploying Laconica within an enterprise can help employees from different parts of the organization share information, Prodromou said. The software can partition off different user groups for collaboration, or have users communicate with the world—or organization—at large. Organizations can also set up conduits to personnel at other organizations running their own microblogging services.
Audio of Evan talking about Laconica at FLOSS weekly
I met Laconica founder Evan Prodromou at Wikimania last year in Taiwan. Evan is also the founder of Wikitravel.