I go to the gym 5 days a week, and can see that happening at the place we go. That guy was pretty small (Even though I've seen alot of small guys lift weight that surprised me many times) to be lifting that much! GG Spotting!
Edit: I just read the info on the video... IMO, the spotter shouldn't have let go of it so quick. I could see the whole "Friendly lifting competition" thing, but when you're pushing that much weight I'd want to take as much precaution as I could and NOT try a new grip. Good thing he didn't suffer any injuries.
That actually happened to a football player for USC at the beginning of this season... a running back I think. He was weight lifting with the strength coach as spotter and the bar fell on his throat. He had to have all kinds of reconstructive surgery because it crushed parts of his larynx.
It would have never happened if he had his thumbs on the other side of the bar(not the same side as his fingers). Sometimes Big Gunns benches like that to put more pressure on his triceps, but this knucklehead was bouncing around too much.
Yaaa grip is important. I was at a weightlifting comp and didn't have a good grip when I was power-cleaning, the bar twisted in my hand and tore of my calluses, blood was a factor lol