When something unfortunate happens, whether it's a car accident or someone making himself look foolish on a thread, we all tend to bottleneck to watch the carnage. Why? O_o
Most, not all, are drawn to accidents...maybe in relief that it is not us or our loved ones, maybe because we live in small towns and worry who it is...I don't really know why.
As far as people melting down, many do take a perverse pleasure or schadenfreude, as ozgirl said, in watching that unfold.
Sometimes I think it's because they stopped making movies like Mary Poppins . A lot the movies and video games are violent these days so maybe people are getting de sensitized. But then again I can remember my parents slowing down when they drove by an accident so maybe humans have always had a morbid curiosity. Not sure about the tread thing though - getting out of the bottle neck and not being part of the carnage can be a simple click away. Cheers!