Theme-park MMOs are consequence-free zones—unless you get into the kind of behavior that is against the TOS, but even then the worst punishment is being kicked off the game. It’s not a problem that theme-parks don’t have serious consequences for player character actions within the game mechanics because no character has an impact on the world. Regardless of what you do (barring some very rare GM-run events) the same mobs will continue to spawn in the same places and the same quests will be done by different people without interruption.
As soon as you give the player the ability to take actions that have far-reaching impact on the experiences of other players, you need to instill a conception of consequence in the player’s mind or face a blight of sociopaths actively ruining the game.
The basic building blocks of dynamic worlds are the actions of the players as they interact with one another and the environment. These actions have meaning in that they change the behaviors or capabilities the environment—both the simulated world and the players that inhabit it. Players need to have feedback from the environment as they interact so that they can learn the rules of interaction and the extent of their own capabilities.
Feedback can be supplied in two ways: in that the players sees what effect his actions have on the world, and in that the player sees how he should feel about that effect.
All games give feedback in the first form. You push on a crate and it moves in the direction you pushed. Simple feedback like this teaches you how to interact with your environment and helps you construct a mental image of tools you can use in further problem-solving endeavors. These rules tend to be too simple in MMOs and this feedback is too minimal, but this feedback’s existence provides the underpinnings for the second kind of feedback.
The second kind of feedback is less common in MMOs. Usually single-player games have NPCs that will react to the player’s actions by interacting with the player differently. The way NPCs react to the player suggests how the player should feel about what they are doing in the world. If the player is behaving badly (in a particular social context), NPCs react with shock, horror, and derision towards the player—the player is supposed to feel this about his actions and adjust them. Because NPCs in MMOs are generally worthless cardboard cutout quest-givers, their reactions have no importance to the player—even though through executing the quest-givers will, the player has interacted with the world in the only way possible in the game, the player doesn’t care about the NPC and skips through quest text. NPCs are just tools used to move forward, to get to the endgame and do the real business the game brags about, be it raiding or PvP.
When the player interacts with other players as his main means of playing the game, either through direct interaction or through effecting a cohabitated world, the tools required to show the player how he should feel about his actions are altered beyond recognition. No longer are NPCs the central focus of the game—players have to make moral judgments about other players. The quality of those judgments has an impact on how much fun each player has.
Through making moral judgments, players establish de facto tribal societies. Once in the context of a society, players behave in regimented, sensible ways while relating to others in their society. The player who acts out will be stripped of his status within the society and will not be able to take advantage of the facilities that society provides, so players are incentivized to conform and contribute. The relations built through this socialization keep players hooked into the game world and happy. PvP is contextualized into society versus society warfare, not meaningless and random killing.
Accountability is at the center of the social and moral systems that form the backbone of player-driven, dynamic worlds. Developers have to provide tools to allow players to hold one another accountable for their actions. Developers need to build tools to track the behaviors of players and reveal important details to other players in appropriate places, building a framework for players to establish crucial trust relationships. By giving players the power to avoid untrustworthy or uncooperative agents, developers can give their players a world where actions have meaningful consequence without the world falling apart into a chaotic mass of criminality and complexity.
Accountability is the social currency of dynamic world MMOs. In order for a player-driven dynamic world to succeed, mechanics must facilitate accountability.