Joi Ito on address book roulette:
It originated with business cards, but has moved to mobile phones. There are three people: two players and a judge. The two players pick someone from their address books and reveal them to each other simultaneously. The judge decides which one is more famous or important. The loser has to shred the business card or in the case of mobile phones, delete that entry from the address book. It’s quite funny because you try to play important people to beat the other person, but if you lose, you lose a valuable phone number. The judge’s perspective of what sort of person is important also comes into play in an interesting way.
It’s no fun when you have backups of your phone numbers, but in Japan, where most people don’t backup their mobile phone numbers, it’s often for keeps.