This looks a lot of fun and potential rich uses within the coporation – a Twitter like tool for internal comms called Yammer –http://www.yammer.com/
The big concern has to be security! Many years ago on a project, I looked at SaaS for internal comms and in one instance we thought a hole might be needed to be made in the Firewall to get the data through, which was a big no-no. Luckily we got round this with https and a lot of converations with the vendor and the security guys.
This service looks like it relies on purely text data being added to the system, but how to ensure that users don’t do anything silly or that the data is encypted?
My motto here is simple – can it be trusted with bank account data? If not, tread with care: I can see enthusiasts jumping in and ruing their acts later…