I’m going to be the guy that kind of disagrees. That individual that deadlifts 800lbs is likely competing at some level. Even if they aren’t, they have spent many hours under the bar learning the lift and finding their groove. Also, comparing a deadlift to a swing is much different. The deadlift can go wrong, but the only forces involved are vertical – the bar only goes up and down. The swing (whether heavy or light) is entirely different. First, it is ballistic. Second, it has a deceleration phase. Third, there is a horizontal componenent to it.
The more precise terms are that deadlifts involve more compression forces and the swing involves more shear forces. This is more of an issue for the spine than anything as far as I know.
For form, watch Bill Kazmaier, especially his deadlift attempts (the first one is red lighted, and he lowers the bar very slowly in the second attempt just to show the judges).
http://www.youtube.com/watch?v=k4FMbKDSc_I
He has a shoulder injury in this video, yet, his form is great. But I think the issue with form degrading in max lifts is not the form going, but the effects of a heavy weight. The effect of the weight on the body makes a difference. For example, one can do a press the same way with light and heavy weights, but the effect of the weight on one's body will cause some visible difference.
So, I do not think "form" truly degrades in the heaviest lifts, just that at a certain point, there is a visible difference in the body under a heavy load, but the form must be perfect.
I am not a fan of two handed swings. Either the weight is too light and it is just cardio work, or the weights are heavy, and putting massive shear forces on the spine. The
weightlifting swing and
GS swing are very different, and the hardstyle two handed swing is a weird hybrid.
(Yes, I know of all the hardstyle swing studies and such, but I do think that is a roundabout way to get the benefits of what one is doing.)