I tried to make my third content chapter, but it's a toughie. What's worse, it covers much of the same ground that Raph is covering here and here, but from a different angle (and much more tersely).
You see, there's a couple of connected "bits" here. "Trust" is one thing. "Interaction/Friendship" are another thing. "Exploration" is another thing. But all three are intrinsically tied to social networking.
One of my favorite game designs (of mine) is a game called "Spider Space". Utilizing a unique resource allocation system, it encouraged a kind of social networking which would hopefully lead to high-trust environments. But more than that, it would lead to high-interaction (friendship) environments and high-exploration environments.
Because all three of these things are related, and all three of them are related to content creation.
A social network is one of the kinds of player generated content that all massively multiplayer games have. I don't believe it is possible to keep players from forming into social groups, whether you call them guilds or clans or shmurgies.
The key here is to remember that content is a living thing. Rather, it's intended to be a living thing.
Content created by a developer is not really a living thing. Players will waltz through it, barely affecting it and barely being affected by it. If they go back it is more of the same.
Content created by a group of players, such as a social network, is a living, adaptive organism. Interacting with it keeps players entertained and coming back.
Similarly, all the things you might think of as player generated content are really just symptoms of the real content. Someone creates a new quest, or a neat-looking car. You say, "yaaay, another piece of content!" But it's not. Not meaningfully. That car, that quest, it's a tiny blip. And chances are, it's a meaningless blip, since it is a waste of time compared to the very best quests and cars.
The important part of making a car or a quest is when people say, "that's really cool! Have you thought about putting in hamsters?" or "that sucks, I bet I can make a better one."
That's the content. The content is the part of the game which draws the player into making the little pieces of piffle. They aren't the best pieces of piffle. They're probably wastes of time. But the act of creating them and being challenged to do it better - that's the content.
That content is enabled by social networks more than any other thing.
You can encourage players to do it better with game mechanics, of course. Most games do this - "levelling up was cool, wasn't it? Now try to level up again!" But that's a shallow method. It (A) doesn't appeal to most people and (B) is tightly constrained and limited.
Using a social network for this kind of encouragement gives a stronger feedback system and a much wider variety of useful producables. In short, it provides better, stronger content creation loop than the insignificant "level up and choose equipment" content "creation" loops in most games.
But a social network needs to have a few features in order to encourage content creation. These features are always the same, regardless as to what kind of content you allow your players to create.
A) Trust. Yes, trust is a critical part of content creation. There are two ways to enhance trust in this kind of environment. The first is to make the ruleset support zero-trust interactions. Like contracts or trades. The second is to keep track of good and bad interaction records - but be careful, that can be farmed and griefed without much difficulty.
B) Interaction. Trust isn't the only important detail. Interaction is, if anything, more important. People will learn who to trust through repeated interactions, even if they don't have any real "trust support" system. But people who don't interact won't interact. So your system has to reward interaction. Not just creating content, but finding content others have created. Not just talking, but talking meaningfully about content. This needs to be balanced, however, because it can easily lead to swamping popular creators. Hence...
C) Membership Control. Your social network is only a help to you at very specific sizes. If it is too small, it is useless. Too large, it is full of noise and gets in your way more than helping you create content.
Therefore, you need to have a way of (A) getting people to have significant social networks and (B) keeping them from being assaulted by every fanboy that notices them.
The so-called "LFG" syndrome falls under here. People without an adequate social network stand by the sidelines, unable to proceed until they get some useful interactions. So they shout, "Looking for group", and cross their fingers.
You need to have something that draws people into social groups. Something which makes even useless newbs into something useful. Simultaneously, you have to have something which gently keeps people from swamping one content creator - both for the sake of that creator and to allow for greater numbers of content creators.
Spider Space had all of these. These ideas really aren't new to me, but they are the subject of chapter 3 of content creation. However, this chapter doesn't taste all polished and textbooky, does it?