Office videoconferencing has been limited by corporate bandwidth and the dismal state of USB webcams ; there's no practical solution that enables one to share whiteboard work over a video link for example. Even so, I've recently been persuaded that for many people, including me, even crummy low resolution images enable better social interaction and higher quality communication.
So I've started using a webcam with Office Communicator 2005. Unfortunately the people I communicate with don't usually have a webcam, so it's one way. They see me. I either see a blank space or my own face.
That's where I made an interesting discovery. It helps me, when on a phone call, to see my own face. It helps me be more patient, and even to be a better listener. Of course, as Emily points out, a mirror would have the same effect -- but a mirror in my office would seem a bit .... odd.
So I'm experimenting with viewing my own face and body language when I'm on voice only calls. I'm guessing it will help me be more conscious of my own reactions, and better able to manage the call.
I suspect this might be a bigger help for people with geek-genes than for non-geeks.
This would make an interesting psychology study btw ...
(I'm sure someone has written about doing this with a mirror in the "old days". One could probably use an iPhone with "mirror" wallpaper in place of a physical mirror or webcam.)
 BTW, the built-in Mac webcams aren't the equal of the much mourned firewire iSight (best webcam ever) but they produce much better results than my Microsoft LifeCam. It's not just resolution, it's also video rate, color balance, focus, white balance and, above all, adjustment for variable lighting.