In theory, the fact that any random person on Earth is connected to another random person on Earth by on the order of six links is amazing. Like the song says, it's a small world; everyone, more or less, knows everyone else. In practice, with smaller groups of people, all the interconnections wreak havoc with weekend party planning.
You obviously can't invite so-and-so and whats-his-name because they used to date but now they hate each other. Those two worked at the same place and had a falling out so we can really only invite one of them. Whats-her-bucket made disparaging remarks about something someone else really cared about. Whosits laughed at a joke he shouldn't have and we can't have any awkward silences as a result of that (oh, and his girlfriend can't come either then). She fired him and now he works at the same place with this other guy that recently divorced this woman that everyone else adores...can any of them come? A misunderstanding from three years ago festers still; two of the three involved will be uninvited.
Solving GRE logic questions are easier. Tom is Anna's sister's great-grandmother's daughter's stepson's cousin's aunt's neighbor's gynecologist's mistress's favorite football player. If Anna is Frank's second cousin thrice removed, what relation is Tom to Frank's dentist? Piece of cake compared with the matrix of possible party guest list permutations.
As a friend told me recently, "I'm too happy in my life right now to deal with all this." Amen sister.
