The invasion of privacy in America has lost most of 
its meaning in the acoustic age of resonance. In 
Russia espionage by ear is normal, whereas spying 
by eye is considered an atrocity. Privacy, however, is 
basically the concern of the visual man and is not 
much known to people of the ear. Another way of 
putting it is to say that the acoustic invasion of 
privacy is subliminal and total, whereas visual 
privacy is strictly limited and enclosed.

Marshall McLuhan, “The President Who Was Not in 
Touch with the Present,” unpublished, 1974.