There's something important to mention about guiding players.
I'm very good about guiding players, at least in person. This has made it very clear that guiding players not in person is significantly more difficult.
For example, players will naturally gravitate towards points of densest simulation, starting with the kinds of simulation they're most interested in. In an in-person game, the GM makes this shit up as he needs it. The player says, "I want to get past the guards by pretending to be a hallucination". Good, fine, run with it. The player loves that kind of stuff, win or lose, because it's a very flexible point of simulation.
On a computer - or just not in person - this sort of encounter is dictated by a hard set of rules which probably doesn't allow for that kind of flexibility. The player, disappointed, turns to other areas of high simulation.
Recently, this has been in the area of personal fashion. So many games allow you to dress your character. This is because it is easy and automatically balanced, while simultaneously allowing the player into a high-density simulation. Good stuff, but it doesn't mean that players like to dress their characters. It means that players like areas of dense simulation.
(Certainly players like dressing their characters. I do, at least. But it's just one of the zillions of interesting things I could be doing.)
Of course, when contained and constrained like in a computer game, players will run amok. They'll push every simulation boundary. The simulation boundaries may be quite strong, so the only place the players can always push is in their interaction with other players.
Pushing that envelope means being a total biter.
Most people who aren't me are nice people in person, on a day-to-day basis. Pushing that simulation means being a not-nice person. It could also mean getting what you want without going through the slow bits getting there, but if you're interacting with real people, that can't be done. So it's jerkface time.
Look at a few examples. Like most MMORPGs on the market: not much in the way of flexible simulation. Pretty poor, in fact. Customize your character in a way which takes all of two minutes to master. Customize your look in a way which may take ten. Sure, the actual act of getting the things you want may take years, but deciding what is better takes thirty seconds.
Other than that? Player interaction. It's the only detailed, highly varied simulation.
Compare with SecondLife (always a fun comparison). Detailed simulations: clothes, vehicles, architecture, games, programming, art, economy, parties, sex. Player interaction? You bet, but it's used mostly as a way to push the edges in other simulations. The people on SecondLife are, by and large, very nice people. This is because they have other realms to explore!
How do you arrange for this in a multiplayer game? How can you create something which is a dense enough simulation to entertain? That sounds hard!
In fact, it's impossible. You cannot create a dense enough simulation to permanently entertain a player.
What you do is you hook the players together in such a way that they create their own simulations in the sparking gap between them. For example, choosing your costume is fun because, in your mind, you have a deep set of preferences about such things. The real joy comes in when someone goes: "Nice costume! Hey, could you make something for me, too?"
That moment is an intense moment for the budding artist. Suddenly, there's a whole new simulation: providing clothes for other people. Pushing that simulation will entertain the player for the forseeable future.
Your job is to provide that connection, so that players can create their own simulations. You give them tools, they use those tools to fill the space between players. Content creation.
This also ties back into my recent posts on gameplay vs story. These tools are not, on their own, gameplay. They are tools. However, since they are wedged deeply into a game world, they are tools specifically to serve the game and hence are made into gameplay. They are what some people might call "story tools". I would call them "idealized gameplay" - something which allows players to introduce new and unique creations into the gamespace.
This method is a great way to keep players from being total biters. It is also a fabulous way to extend the life of your game. Done correctly, it doesn't even have to be all that risky or full of porn.
(Apologies if you saw the first draft of this essay, I accidentally hit control-S. Honestly, why is that there? The number of accidental publishings must exceed the number of people who are really glad they can push control-S rather than click on the button...)