Yammering

Yammer the TC50 winner is a microblogging tool for companies. It perfectly quick broadcasting of knowledge resources across the organization. For more detailed discussions, it will need something else (wiki, forum, blog) integrated so as to seamlessly break into a topic instead of just giving tiny urls.

The key thing lacking is grouping and having a user as part of relevant groups. Integration with file sharing ability could well make it extremely useful and justify its pricing.