I'm a visual person so the great graphic below from Ji Lee really appeals to me, but however you choose to process it I thought this was worthy of some time to reflect upon.
While there is certainly a difference in the levels of intimacy between many of these forms of communication, in my experience the intimacy can vary greatly within any one of them. So I'm not sure I see these as levels of intimacy so much as a reasonably comprehensive list of the choices we currently have for communicating with each other, mostly one to one in these examples.
When you consider how recent many of these ways are you can see why I expect the growth of our communication choices will continue to be exponential. So one of the critical competencies we need to develop and improve is our ability to match the communication "medium" with the context of any given need and situation. When is a Tweet the best choice, or an Email or a hand written letter or a phone call or when do you need to go talk to someone in person?