Microsoft, for example, is testing OfficeTalk, a microblogging service that's a sort of Twitter for businesses, while Google has been using an inside-the-company version of its Google Buzz feature to allow co-workers to share information with one another.
I still don't see Twitter as any sort of technological leap, if anything it's the opposite and works like a late 1990's version of ICQ with the privacy turned off and all messages viewable by everyone.
What Twitter has that ICQ didn't is web access, you don't HAVE to download software to use Twitter, but BY FAR Twitter has less features so... Is keeping things as simple as possible the new high tech?
OfficeTalk and Buzz will have a hard road to climb because they're late to the show and will be hard pressed to make something simpler.
Twitter isn't a technological leap. But people wanting to share more information on the internet is a big shift in privacy perceptions. Twitter happened to be in the right place at the right time for this.
An OfficeTalk license is $12,500 for 100 people. This assumes your using MSFT Office, already.
Buzz is a useless mess still.
The internal social network software I'm most impressed with is Yammer. Its cheap/free, feature rich, and easy to use.