Most vehicles have a weakness. I had a 98 Dodge Ram. There problem was the bottom of the doors. Rust would get started on the inside by the weather strip, and be hidden by it. It would then spread, and if not taken care of, spread to the outside bottom of the door. It was only surface rust, but it would spread like crazy if not stopped. Road salt is a big part of the problem.
Another example is late 80's to late 90's Chevy trucks. The cab corners, rockers and rear wheel wells are the worst areas. I have a coworker who had his fixed several years ago, and its started all over again. His problem is that it got into the frame also. He keeps on driving it, its got something like over 200,000 miles on it so he got his moneys worth.
Vehicles are much better than they use to be. I've restored a couple of 1970 Mopars and they were very vunerable to rust, as were a lot of other cars from that era. Plugged drain holes was a common cause.