So I've noticed this a few times and wondered if anyone else had. There's quite a long thread on here quite recently (I won't say which one as it seems to be dying down now) where one minute everyone is YABU and the next everyone disagrees.
It seems to come in waves, this particular thread had started off with everyone thinking the OP was being reasonable. Lots of supportive comments until someone else disagreed....YABU. The thread was then filled with YABU comments for a good few pages, some not nice comments at all. Until one disagreed and it was back to YANBU.
I appreciate long threads are a ball ache to read through and you tend to always read the last comment posted before yours but I can't help thinking of half the views are more just agreeing instead of your actual point of view on the topic.