ScottG13 - 1:13 pm on Mar 25, 2010 (gmt 0)
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.