"If you tell everyone your'e going to game X, don't try to trick everyone and secretly run game Y."
For all values X or Y.
Too true, no matter which side of the Swineyard fence you sit on. It's the classic "GM's Dilemma":
GM: "Guys, I bought this new game last weekend. Can we take a break from our current campaign to play it?"
Guys: "Uh, no. We like the game we're currently playing."
GM: "But I'm the one running it for you guys. Don't I get a say in what game we play?"
Guys: "Sure, but if you want to play a game that we don't want to play, that doesn't mean we have to play it."
GM: "Dag-nabbit, guys! C'mon...!"
Guys: "Whatever, dude. I roll to hit."
!i!