Those were the days - Mary Hopkin -1968

http://www.youtube.com/watch?v=7duLVZC8eh0

Dunbar's number

Dunbar's number, which is 150, represents a theoretical maximum number of individuals with whom a set of people can maintain a social relationship, the kind of relationship that goes with knowing who each person is and how each person relates socially to every other person

http://en.wikipedia.org/wiki/Dunbar%27s_number