Matthew has written an interesting piece on Japan, inspired by Lost in Translation. It is the 12-15-04 entry [link ^[1]]. Matthew provides an accurate description of Japanese social life and loneliness:

Tokyo is a city where most of the population is lonely. Every Japanese has a tight social circle to which they belong and it is their life be it their company or high school friends. Different social circles do not mix.

I would like to add that there is some negative karma associated with being ostracized from your circle. Which is probably why people cling to their circles for dear life.