Facebook has produced a map which shows the geographical relationships between its half a billion members on a global scale. Paul Butler, an Intern on Facebook's Data Infrastructure Engineering Team, produced the visualisation by plotting friend relationships between pairs of cities. In a blog post, Butler explains: "I defined weights for each pair of cities as a function of the Euclidean distance between them and the number of friends between them. Then I plotted lines between the pairs by weight, so that pairs of cities with the most friendships between them were drawn on top of the others." [Agenceis]