I have 'baited and switched' once, but I'm not sure it counts, as nothing really changed. The (D&D 3.5) party was using wish from one plane back to their home base. I instead sent them to a 'Mirror, Mirror' type universe (complete with evil goatees) and they had to find another way home. Everybody thought it was cool, so no worries. Nobody got the goatee reference, though.
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I wouldn’t call that a bait & switch; more like a correctable plot complication – those I have little problem with. I tell the difference based on (a) the premise presented to garner interest to start play varies wildly from presented situation and (b) the chance the players have of converting the game play back to that premise.
Here a couple the more egregious personal examples of bait and switch:
Campaign pitch: Traveler-like universe using HERO system, PCs will be crew of a science research vessel looking for time travel possibilities.
Campaign result: 2nd session all players are together, the universe is destroyed and the surviving character are transferred (and converted) to Chivalry and Sorcery world. Players of unsalvaged characters made new ones using C&S rules.
Campaign pitch: Aftermath campaign using the default roll-up system starting in the Mississippi delta region.
Campaign result: PCs are in a 20-mile wide bubble on a Starlost-style ark ship. The fact one PC’s background had him as a fighter pilot based out of California was waved aside as “implanted memories”.