Wow, Yammer's UI looks, uh, a lot like Facebook's.
To put that into context, by "won over" they mean that at least one person working for that company has signed up for it. It doesn't mean they use it. It doesn't mean more than 1 person has ever checked it out.
Still really impressive, and using work emails to create an instant network is really smart.
Funny, isn't this the same company everyone was predicting would #fail because it was "just another clone of Twitter" but for companies? Well, while they still could fail, they're getting away from that the longer they're alive...