I take it you've never used Yammer, which was created as "Facebook for work" seven years ago. The Yammer news feed is actually a great way to stay generally aware of what's going on in your company across lots of different groups or functions. I'm an engineer and its nice to see what sales and customer support are worried about from time to time and occasionally chimein when I can be helpful. At my company we use chat for quick, immediate conversations, and Yammer for bigger, more in depth conversations about product or architecture or various business tactics.

I imagine Facebook for Work would happily fill a very similar role to Yammer, sitting comfortably alongside chat. Of course, they'll probably have a much easier time with distribution given the brand recognition.