Based on where you currently are and who's in your contact list, Apple's new iPhone looks for nearby contacts. This is possible through the built-in GPS module and the contact list if it has addresses added.
Future Vision by Erwin Van Lun on this article
All information will become increasingly more available in real time. Most people have to change addresses etc themselves when they get an email of someone who moved. Soon this will be automatic. With your social network in your pocket you’ll be walking through a strange city, past the door of an old acquaintance who’s moved five times by now. Quite something to be able to just ring the doorbell…