The Ford-Firestone failures are the perfect example of why I rarely keep oem tires on anything, especially up here since road conditions are so poor. Load capacity had far less to do with the failures, a cheap, poorly built tire with owners rarely if at all checking the vehicle's tire pressure or even looking at them, is the combined fault. I am amazed how many people drive on failing tires, I'm always pointing out separations, low pressures, sidewall bulges, lack of tread, etc.
OEM tire pressures are not for handling, milage, comfort, even tire wear, they are defining where you should be fully loaded to the vehicle's capacity. My older super duty spec'd 70psi rear, empty or loaded. Rediculous, ride and tire wear would be horrible when empty, but it protects the manufacturer if I run less psi while fully loaded and have a tire separate.
I've used a huge span in tire psi with various vehicles, 10 ply tire on a f150 doesn't make traction worth beans if you use the 35psi fr/rr rating in the winter, an '03 windstar running 35psi on oem uniroyals look like they are running an inch of sidewall on the pavement, and feel that way too.
Many different factors define proper psi, what is on the door may or may not be the best recommendation, but it is sure hard to get around the stupid low psi warning systems in all the new vehicles now while trying to find optimum psi, LAME!!!!!
Us mere mortals don't get that level of service.
Then there's the little problem that the numbers on the placard aren't necessarily what the engineers wanted. 
