We are all familiar with the real world impact of "presence" - and the powerful clues to social context that it provides...

Ok, ok, some examples.

Do you think twice about entering an empty restaurant surrounded by thriving atmospheric venues?

Do you feel a lift in adrenalin at one of the world's great sporting venues filled to capacity with screaming fans? (I was lucky enough to be at the Melbourne Cricket Ground in 2005 for the mighty Swans victory...).