>"hey, do you mind if I go through your address book and contact all your friends and family and ask them to be my friend too? If you consent, say, 'what' or 'huh'"

At some point I spent some hours to investigate how they did it and trying to tell google (gmail) to not let Linkedin do it (again?). Not sure how much success I had. I think it is a mistake/problem of Google to allow such things.