Fairness and balance

1. Premium Currency vs Free Currency (Virtual Economy Gamification Tips)
2. Virtual Store vs In-Game Store (Virtual Economy Gamification Tips)
3. Buying Power vs Spending Power (Virtual Economy Gamification Tips)
4. Game Modding vs Game Hacking (Player-Centric Gamification Tips)
5. Rewards vs Incentives (Player-Centric Gamification Tips)