Facebook just rolled out this feature a few days ago. That was Google+'s major edge to me but it would have needed my whole network on it to be useful.
Now that facebook has it, it is going to be very hard to get people to use something else.
Now that facebook has it, it is going to be very hard to get people to use something else.
The other person has to agree to that, being identified as family or a coworker on your profile.
Not being put on a certain list.