It's an interesting thought, and not a new one-- just as we have morality in the real world, our virtual worlds also have their own codes that can be upheld or broken. Shwayder speculates, however, that this morality requires PvP-- players can only uphold the morality they've put in place if they have the option to control other players by ganking them. But I'm not so sure that's true. There are definitely ways to define behavior in a PvE environment-- guilds are one way these rules are passed around. Each guild has their own rules, and if those rules are broken, guilds (and even their allies) can blacklist players or punish them by not allowing them to enter into group raids and other places where the best rewards can be found.
Every society, real or virtual, has their own set of codes to live by, and it's very interesting to see how these are propagated in a virtual world. Whether via PvE grouping, or PvP retribution, every game has its own set of MMOrality that new players have to be taught in order to thrive and flourish socially in the world their characters live in.