When Buffy got thrown out of her house in season 7. I won't say why because it's an essay (from things said to it happening at all). However, the very first time I saw it I backed it up to watch it again as I felt I must've missed something, and after that I figured it was some dark spell at work (which would make sense, the First would definitely help Amy, and probably vice versa, and the Bringers also did magicks to help torment Angel in season 3)....but no. We the audience were supposed to accept this as a natural event that incorporated knowledge of the characters and previous seasons (and just common sense), but I just can't lower the bar that far.
'Course lots about season 7 bothers me and I'm convinced most of the writers weren't even trying anymore other than to get it over with as they were trying to move on to other projects.
But after season 1 I think I was about able to accept any craziness, which later seasons added to. I usually went with it. I can nitpick a lot, especially from season 5, but I believe the writers were still honestly trying (at least until season 7 Buffy) and I could see what they were going for. Just that one scene of Buffy getting kicked out and it not turning out to be some kind of dark magick had me going, "Utter BS." That's why I'm probably the only fan that doesn't get mad at anyone over the scene, because my brain refuses to accept it as legite, and I get the feeling some 13 year wrote it who had forgotten much of the previous seasons (at least before season 6). Instead, I get mad at the writers--not for writing something I don't like, but for writing something so ridiculous that I can't even accept it on Buffy.