We also ran a pilot of Metasight in Syngenta in 2006. Like Mars, we also liked the product but the pricing model was prohibitive. We also had serious concerns about data privacy.
We have been looking further at Sonar from Trampoline and are very impressed with it - we may be doing a pilot shortly. This time around the lawyers seem more relaxed about the data privacy question. Also Sonar allows the user to choose which topics he allows people to know that he has an interest in which helps. Also, unlike Metasight, Sonar can draw on information other than e-mail. This means that one could start a pilot drawing on information that is already declared 'open access' e.g. Blogs.
We are also looking at Illumio from Tacit which has a very different model whereby it works out who is interested/expert in what and then routes questions to the appropriate experts.
Autonomy also produce some tools - see attached documents