Circle of friends

Interesting LJ entry by a fellow IgorMUD player:

Anyway, Dunbar did some research and concluded that our brains have enough cognitive processing power to keep tabs on a maximum about 150 individuals. That’s everyone, from your family, to neighbours, work/school colleagues, friends, friends of friends, family of friends, your postman, local shopkeepers… it also explains why people in big cities are so impersonal. You could run into 150 people on your way to work - very possibly on a tube train carriage (the way they’re crowded during rush hour, it wouldn’t surprise me).

Now have a look at your own circle of friends, your list of email addresses, etc, and figure out with how many of those people you are really keeping in touch?