From Social Patterns
Technology can be cold and impersonal. When the concept of a “ghost in the machine” first arose, it was used to deride des Cartes’s mind-body dualism, ridiculing the idea that the body is a simple meaty mechanism and the spirit is some ghostly presence that imbues it with humanity. Dualism has fallen out of fashion in philosophical circles, but the truth is that in today’s online social systems there is a fundamental duality baked right in. The machinery connects us but without the human presences (the ghosts, us), it is simply a tangle of wires and electronic impulses.
In the real world, we like to know that there are other people around, coming and going, adding to the life of a place. An abandoned building is scary. One that has signs of life can be much more warn and welcoming. There are a number of ways to communicate this sense of life in a social interface.