My litmus test if the load is secured properly is to drive down my crappy driveway. If it doesn’t come loose when I check it at the end, I’m good for the speed test on a real road. If it then doesn’t flutter in the wind, I figure I’m good.
In all seriousness, I overstrap the heck out of everything. If the state (Louisiana) require two chains for my equipment, I put four. Maybe that’s because I’ve not only been stuck by a flying piece of plywood when it hit my windshield from someone’s load, but also because I watched a tractor roll off the back of a truck in front of me when he went up a hill, barely missing me as it rolled to a ditch.
So, yeah, the I believe the vehicle operator should be held responsible for his load, accident or not, and the seriousness of the punishment based on the actual end result.