I've got 3 to add here.
First one happened at my home hill. They have two T-bars running side by side, and my brother and I were riding up one of the two, when we heard this snap, and a grinding noise. Over on the other t-bar, one of the t-bars had come off of the cable, and was sliding backwards down the cable in a shower of sparks, with a pair of scared looking older guys holding on for dear life. Finally, they ended up slamming into the t-bar behind them.
the second one happened on a school trip to the same hill. My friends and I were riding up the chair, when one of them yelled at this girl who was learning to snowboard and was straightlining down the main run out of control. When my friend yelled at her, she looked up the chair we were on, the nose of her snowboard dug in, and she ended up doing 4-5 cartwheels down the hill before sliding to a stop.
final one happend at marmot basin, my brother and I were riding the t-bar because it had no lineups, compared to 5 or so for the chair. since there were no lines, my brother and I were riding seperately, behind this group of 3 girls on snowboards. Those that have taken that t-bar know that it starts off pretty steep before flattening out, and just as the first pair of girls got over the steep part, one fell, and managed to hit the girl who was on the t-bar with her. The two of them were tangled up sliding uncontrollably backwards down the t-bar path, and they hit their friend, and all 3 of them ended up sliding down the steep part towards my brother and I. My brother didnt have enough time to react, and got hit too, but luckily I got outta the way. By the time the ball of people reached the bottom, 8 people had fallen/been hit. The sight of the mess was so awesome I couldnt function from laughing so hard for about 5 minutes.