define a real friend

In the last few weeks i had a lot of meetings with start ups and some of these start ups, like so many around these days wanted to know who are my friends, Which lead to a really good question who are the users friends?
Does my social network friends are my friends or are they just contacts?
maybe my contacts/phone book will be a good place to find my closest friends?
Basicly the bottom line is How close are the social networks friends?
it's a good question with a simple answer (not that close...) being a social network friend is real easy... and usually only 4-10 "friends" in your friends list are real friends.
so if you want to develop a service based on real friends... you need a good method to find them (importing the friends list just doesn't good enough)

Navot