Of course there is friend on Facebook and there is Friend, but beside me and the friend in questions there is no one to quantify that relationship. And I'm sure letting users explicitly quantify relationships on Facebook will be supper annoying and not used by most of the users in much the same way they don't use Friend List. What Facebook can do though is to approximate this quantification.
A friend who has 100 friends is more likely to know and have something in common with me than a friend with 4000 friends. In other words this also means that the more friends I have, the less I value each of the particular friendships (on average of course). This is why having 1 friend in common with someone who has 10 friends makes me more likely to know that person than someone with whom I have 10 friends in common, all of which have 1000 friends. Just a suggestion for friend suggestion.
