[0des]

This is a common technique used in film when someone is reading from a teleprompter. It is meant to draw attention away from the speaker's eyes moving from side to side.

[billyhoffman]

Which makes the Apple presentations all the more impressive. The camera is head-on, but I don't notice anyone's eye's moving as if reading a teleprompter. I think they've memorize it

[threeseed]

In Apple's presentations they are almost always far away e.g. several metres from the camera.

If you look at Craig's OSX section where he is closer you can clearly see his eyes slightly move left to right as he is reading from the teleprompter.