The article states that there was a safety net that was supposed to stop them. Instead it ripped and let the ball roll on down the mountain. I can't blame the people in the ball. They thought they were doing something fun. Obviously safety was a questionable term in this case.
I wonder if at any point they took a look at what they were about to do and thought to themselves, "This is a bad idea." I saw the potential for disaster before they even let the ball go down the slope.