Simply being able to see and hear one another cannot be entirely critical. Blind and deaf people can still communicate and be aware of immediate presence without complete audiovisual input. Also, though the telephone can bring audio information, ra rely is one mislead into believing they could "reach out and touch" the person on the other end of the receiver. Despite the sound, there is still the aura of distance.
The aura of distance, or of presence, is something greater than the sum total of sensory information. If a medium could provide information of sight, sound, touch, taste, and smell, in real enough time then perhaps one could be fooled into believing that one who is distant is really quite near. But without all the data, and with each type of information coming separately, proximity is a thinly veiled illusion.
In grade school as children we learn how a classroom situation works. We learn who is the teacher, we learn to raise our hands. More subtly, we learn how to know when we are being called upon. This might include a hand-point, but more often than n ot, it will include eye-contact. Thus far, the media being used for this class has not been able to successfully translate eye contact. This may be because we are not using the technology properly. Eye contact can be communicated if one looks directly into the camera. But this belies our instincts, for there are few of us who truly believe that the camera is the window into the soul of the person on the other end. It is obviously not their own eye. Furthermore, only one person can communicate eye co ntact because if one looks into the camera, they cannot see the person on the other side and be able to read their expression. Communication, as we have learned it, is not one-sided. It is constant sensory dialogue between people that transcends their m ere words. When we follow our instincts and look into the monitor, two things happen to dement the illusion: one is that the slight difference of the camera angle gives the air of unbelievability that the person on one end is truly looking at the person on the other. This is also a two dimensional person, with no turn of the body to indicate which side of the room the person is trying to address. In order to guess the addressee, the people on the other end engage in the second phenomena - they stare at _themselves_ on the screen!
True communication is further hampered by delay. The sound arrives before the visual input of the corresponding image. This is the opposite of what would happen in a conversation between two physically-near people for, as the laws of physics sugges t, sound is actually supposed to arrive _after_ the image. Although the differences in speeds may be tiny, they are still extremely perceptible and the discrepancy confuses the communicators enough to make it difficult to believe in proximity.
There are other problems which undermine the illusion of closeness, such as the lack of smelling input, or of heat, or peripheral sensations of motion. Perhaps the technology could find ways of communicating these too, but the information is still r elatively useless when it comes in the wrong order. We have learned how to interpret sensory input - we know what order it arrives in and how to process it. In theory, it may be possible to learn how to process this new order, and we have already begun to do that. We have figured out conventions to replace the standard sensory input we are used to in order to effectively communicate, and what we have demonstrated is that even though we will not be fooled into believing physical proximity, we are satisf ied that what the technology is able to transmit, the essence of our ideas, is the next best thing.