Playing around with iChat AV has made me think about the context of social conversations that are removed when you use email or chat.
Video links with iChat allow the exchange of the visual subtleties that most of us are adroit at using. The resolution is good enough (at least with cable broadband) that a certain amount of transparency seems to appear after a few minutes of interaction -- the fact that you are talking through time zones and computers seems to go away and you find yourself using more of the visual pieces of communication.
At a lower level one of the main differences between IM chat and email is a sense of presence - you type something and someone on the other end responds. There is a sense of a presence (sometimes I get this when I send an email to someone at an odd hour and they respond within a minute) that clearly influences the conversation. How many times have you found yourself wondering if you are intruding on some other activity on the other side?
I'm sure much has been written on the structure of two way vs pseudo two way and one way conversations. All of the various modes have their place, but there are types of conversation that require a sense of presence as well as audio and visual feedback. Together they stitch together a context for the conversation itself.

Using iChat video makes me think that you could do real story telling over the net and the feedback from the view(ers) would greatly impact your performance.
One wonders how much contextual hinting is required. A nice photo with IM may be a big help. Is there a difference if the photo is obviously current (say if it updates every few seconds or when the sender poses and pushes a button)? How much would such a visual scheme help audio chats?
Apple seems to have raised the bar and made this sort of chat easy enough and good enough that it is a transforming experience. I have been a nay sayer for years noting issues with lip synch, lighting and camera aiming (the eyes of the two users don't exactly meet due to camera position) - then I use iChat AV with an iSight and am sold on the concept in about a week of use. The next few years could be very interesting.
I guess it is time to design a simple lighting scheme for this class of camera.