Today's xkcd has an algorithm that, given a point on the planet, calculates a random point within a certain distance of that and outputs the coordinates accordingly. The random point is based on the DOW Opening that day so each day it is, essentially, impossible to predict where the next day's coordinates will be. They call this geohashing (I always wanted to use that term for something else but whatever). I think the whole concept is very cool. What a cool way to meet people. Here's the implementation of the algorithm in Google Maps.