What are friends for
There is however one aspect missing that I think will turn out to be crucial to it’s succes: uncertainty.
Friendship is by definition two sided. It does not have to be symmetrical (meaning you both feel the same towards eachother) but at least there is to be some level of reciprocity. Most group of friends consist of a small group of people that have a high level of reciprocity and close bonds in their relations to each other. Around that group there is a larger community where the level of reciprocity is not consistent for the whole core group. They are sort of in the group and out of the group at the same time, depending on who you ask.
This foggy definition of a circle of friends is something we as humans need since we deal badly with rejection. This lack of Transparancy makes it possible to create blurry edges for people to feel in while in fact they are only partly accepted. This blurry edge however does create a gradual path for people to move into the circle step by step. This is something we probably all recognise from our own experience, especially during school.
Because of this transparancy in Circles what you end up with is the relationships type in LinkedIn where everyone is a friend since it is too confronting to reject someone as a friend. And when everyone is you friend than no one is.
So unless Google is able to build in a combination of reciprocity and bit of vagueness in circles my prediction is that it will not succeed. If they (or Facebook) does succeed in modelling how friendships works in real life than that social network will win the battle. Because, aren’t we all looking for friends?