I'm not reevaluating based on that frame breaking. I don't know what all the truck owner was doing, but the fact remains there are lots of overloaded vehicles that never break. I think it's more likely that he added more stress to the frame by having a poor suspension solution/worn suspension and/or the type of roads he drove.
That being said, I'm under my GVWR sticker which is 14500. When I first bought my truck, it had 95K miles on it. The first trip with the TC I hit a bump on I-90, and it sounded like it hit really hard. It's hard to describe the sound, but I knew that wasn't right. So, I bought new shocks. The previous owner used it to haul horses cross country with a large gooseneck, and it had regular service based not he Carafe. They obviously didn't think the shocks were worn out ... at least they weren't replaced. All it took was to load the TC, for me to notice it. I have no idea what their pin weight was on their trailer loaded.
In other words, some of us notice things that aren't quite right while others just keep driving. I wasn't driving the truck that had the frame break, but it's hard for me to believe there were zero warning signs if I had been driving. Of course, this is just speculation on my part.
I've seen it before with other vehicles. For instance, my friend drove his vehicle every day. One day, I rode with him and asked him what that noise was. He said, "I don't know ... it's been doing it a few weeks." After I mentioned it, he took it to the shop and all of this front end components were worn and were so bad that the shop told him to leave it. It was ready for a catastrophic failure. Who knows how much longer he could have driven it.
Similarly, most blowouts on RVs aren't really from overloading at normal pressure. Instead, it's usually because they have low pressure. If you are paying attention, you should be able to notice it.
YMMV.