Yahoo Chess Rankings
Design
How would you design your ranking system in an online game? You use points to track the player’s competence. You gain points when you win. If you lose the game, your points don’t change. But the other guy gains points, so his rank goes up but your rank stays the same or goes lower.
Assumptions
1. Fallacy of competition
You assumed that players always work against each other. What if they cooperated and passed the crown among themselves?