There is a dangerous assumption being made that one's "friends" on facebook are people you actually know. There are plenty of people I knew (past tense deliberate) who are serial friend-adders and add people they have never even talked to.
i don't think that's true as most people are in stuff like loops where people are usually connected to others the same people their friends are connected to ex. all my classmates are friends to eachother or the whole family are friends
this makes this review look strange
the minimum number of steps (if everyone had a different friend than the previous one or other branched friends) = log(avg. no. of friends, total facebook users) = log (190, 800000000) = 3.907 i think loops cancel most of that so it could reach 15-20 steps or so (maybe infinite for some people/groups)