Regarding Facebook "mutual friends"

Regarding Facebook "mutual friends": As of today, I am "friends" with 604 people on Facebook. I'm nearly certain that I have met every one of these people in person at least once and many are close friends. I typically only connect friend requests or add friends who I have met in person and have had a chance to at least get to know a little bit. My "friends" list is a mix of family (I have a very large family), friends, current and former business colleagues and acquaintances I know locally and from my many travels in life.

I find it fascinating that with about 80% of them I have anywhere from 15 to 40 "mutual friends" in common. There is another approximately 15% of friends with whom I share approximately 40-80 "mutual friends" and there is an approximate 2.5% with whom I share about 80-100 "mutual friends" and another 2.5% with whom I share about 150+ friends. I find the mutual friends aspect very fascinating, especially the people with whom I share 100+ "mutual friends".  There are even several people with whom I share 190+ "mutual friends".