It seems so obvious, yet Twitter has been around for a several years now and no one has done it yet.
I do think there were other "cooler" companies, but this could be huge. Right now Twitter mostly consists of a relatively small group of web/tech people. Just like what happened with Facebook and colleges, if Yammer gets critical mass in a few big companies, it could explode.
Yammer is far from the first enterprise twitter app. Oracle, IBM and now SAP all even have versions in some form or another, and Prologue, the wordpress based one, has been around for almost a year.
I agree with you that Yammer has the potential to be very huge. I'm not denying that. I'm just surprised with so many innovative minds making up the panel of judges that they didn't choose someone with more of an original idea. There's a great quote from the TechCrunch comments that says "Doesn't the Valley pride itself in innovation?"
I do think there were other "cooler" companies, but this could be huge. Right now Twitter mostly consists of a relatively small group of web/tech people. Just like what happened with Facebook and colleges, if Yammer gets critical mass in a few big companies, it could explode.