Interesting idea.
I like the notion of more public discourse within companies, but my experience is it can go horribly wrong very very quickly. Some of that experience was in fact as an MS employee, and when people accidentally press reply all on a company wide email at a company with tens of thousands of employees and expresses an unpopular opinion things can south very quickly.
It doesn't mention in the description if it allows genuinely anonymous posting/discourse (where your employers cannot identify your posts). Office politics can be horrible and a lot of employees will hold back in a forum like that without anonymity, reducing it's usefulness.