I've bailed on a couple of campaigns. One was at the DM's tiny apartment, which was pretty filthy. Miniatures, books, loose papers, etc. covered pretty much every horizontal surface, including chairs and the floor, and the glass I used to get a drink of water the first time I arrived showed no sign of having ever been washed. At the next session when all the players were present and the game properly began, it wasn't any better. Totally unclean apartment, now made worse by multiple people vying for a clean place to sit. It was hot, and I believe I may have been the only person there who had showered before coming to the game. One of the other players wore a t-shirt with a picture of an anthropomorphic fox wearing boxer shorts with one thumb hooked seductively under the waistband. Also, the DM half-ass winged it the whole game, complete with day-saving super powerful DMNPC characters. Unclean environment + creepy, smelly players + no real adventure = Tewligan's work schedule suddenly becoming mysteriously too busy to stay in the campaign.
Another game I bailed on was a 1e/2e hybrid game with pages and pages of houserules. Among other things, each character got special abilities or perks from an old 3rd party book. My character was very persuasive at lying, which the DM abused on my behalf - I played a slick, smooth-talking character, and whenever I would tell a lie, the DM would roll and tell the other players they had to believe what I was saying. Also, we spent a good part of the first adventure in which monkeys threw poop at our characters while we tried to open a door. He kept rolling for the poop to hit, and saying "Oooh, a big hot handful hits you in the back of the neck!" There was no actual damage, so the rolls were entirely unnecessary and wasted a good 15 minutes of game time. Plus, rules tended to be thrown out and ignored so the DM could just wing it without the burden of using the books. That, combined with the fact that the place was inconveniently far away meant that I had to bail yet again.