Around five years ago an old friend of mine bought a 2006 Tacoma 4x4. He dropped by to show me his truck and while I was looking at it I got down on my hands and knees to look at the underside of the truck.
I was surprised to find the frame rails completely covered in rust. At the time I hadn't heard of Toyota's problem with frame rust.
For comparison, my 2000 Ford Ranger, which was six years older, had zero rust on the underside.