Mandy: Zak's going for a Total Party Kill tonight.
Me: Am I? Let's review...
Connie falls into a pit.
Lady Smashalot over here stays at the edge of the pit and begins a conversation with a Non-Player Character who says "What happened there?"
Lady Smashalot flies into a rage and decides to attack him for some reason.
KK: He was a hippie.*
Me: Fair enough, still, you decided to attack him, you chase him down--into a room full of people he's friendly with--and stab him, and he vomits up a hydra.
Then you ran away from the hydra, then you turned around, ran back and attacked it. Then it ate you.
So, none of that had to happen. I hadn't planned any of that, all that happened because you decided you had to kill a hippie.
Mandy: I was trying to distract it.
KK: How was I supposed to know he would vomit up a hydra?
Zak: Well, you got here by going into a place full of people that vomited random monsters.
KK: Oh, right.
I like my players, and we have fun.
However, I know the way we roll isn't the only way.
I look over at Tao's blog and I find the clockwork world there impressive and inspiring.
Alexis goes in for a lovingly simulated world, where the price of ox feathers in Novgorod is what the price of ox feathers in Novgorod should really be, assuming everything else is the way it is. And there actually is a Novgorod. And there's no ox feathers 'cause oxen don't have feathers.
Some people think these kind of simulatory rules are just there for their own sake, but that's not entirely true--part of the fun of having a world that really makes sense is that if the PCs do things that they'd normally do, then they generate their own plots merely by doing them. And they can plan reasonable tactics because they know the world operates on real-world-like rules.
If the world is simulated enough, then if the PCs, say, build a castle, then paying attention to where they build it might actually matter, in terms of what trade, political consequences, and monster infestations they can expect. And they don't have to worry about game mechanics--if the world's simulatory in the right way, they just need to worry about what would make sense.
I, myself, like that idea. It allows you to play the game on more levels simultaneously--I could kill the orc to get the gold, but if I don't wear a disguise the orcs may start to realize I'm just this guy who's been robbing orc temples for about sixteen months now and I might get a reputation and they might come after me in the comfort of the bed I sleep in where I don't wear armor because if I did I'd wake up with severe back pain and so I'd better hire some bodyguards, but which bodyguards? None of them seem very trustworthy since... Actions have consequences, cause has effect, a story can begin to write itself.
As the death of Lady Smashalot (and Palomedes, and Ilona the Illusionist) demonstrates, not all my players are necessarily the kind of players who would appreciate the behind-the-curtain tinkering that's necessary to create this kind of world. So the world's logic is pulpish at one end, nightmarish on the other, and fairy-talish in the middle.
And, honestly, I don't mind. Every party needs its Pippins. But if occasionally the PCs burn down a town and no-one notices, or the vengeful tree sprites seem weirdly arbitrary about which trees they protect, it's because half the players around here wouldn't notice if I did it any other way.
*He was an anesthetized vomiter. Vomiters, being constantly ill, speak in dazed, distracted voices.