Squats: The greatest of all gym moves, until you load up a barbell with more weight than you can handle and let it turn you into Gumby.
All we're gonna say is that guy has one helluva spine to flex like that.
Because there appears to be some confusion: If you're gonna go for a big squat, then try to get two spotters—one on each side of the barbell, since a single spotter can't do much to help you. If you don't have any squatters around, then work out in a cage with some metal supports that will keep this exact scenario from happening.
Alternatively, use bumper plates (the big rubbery ones). If you find yourself "in the hole" at the bottom of the squat and no one's standing immediately behind you, then simply let go of the barbell and let it roll off your back.
Just don't let it fold you in half.