Rewards are the hoops players jump through. And if jumping through that hoop is accomplished by being a jerk, you’re going to end up with a bunch of jerks. It’s a pretty simple situation. Ideally, you identify the behaviour you want to encourage in your game, and you design rewards to give people who show that behaviour the best rewards.
If you want people to group up, for example, you might offer an increase in experience for everyone involved. And you would offer enough of a reward to make it worthwhile, but not so much that people feel that playing alone is “worthless”. Do you want people to help their friends level up? Don’t penalize them for grouping with lower leveled people.
You can do this in reverse, too. You can examine a game and see what the rewards are to deduce what the game designers want you to be doing. Or look at what gets a player penalized to see what behavior the designers don’t want you to do.
Warhammer Online went through some changes with this concept recently. Many people were playing Scenarios as opposed to going out into the Open RvR areas. By increasing the rewards in the Open RvR as compared to the Scenarios, they found a good way to get people to go out and populate the RvR lakes. And if you look at World of Warcraft, every reward is centered around individual accomplishments, not group rewards. Guilds don’t get accomplishments, people do. This encourages people to think in terms of themselves and not their group. Grouping with lower level characters hurts everyone’s experience point earnings, so we assume Blizzard doesn’t want people to play together unless their levels are within five of each other.
This effect is why so many people feel drama is a fact of life for end-game guilds in World of Warcraft. Everyone in the guild is striving for personal gain. And those who are not, are not playing the game as designed. When you defeat Naxxramas without anyone dying, the guild does not get an achievement, the players do. The guild doesn’t own the guild bank, the guild master does. There is room for the appearance of benevolence, but the truth of the game is that rewards are individual rewards only.
Individual rewards promote individualistic behavior.