The dealer said its rusting from the inside out. They just did one a few weeks ago full bed rapacement. If you google it you will see a pic of one that was cut open, its like a cavity/space under the bed and support. My two worst spots are in front of the wheel wells and one spot behind the left wheel and all areas are on the bed floor.
There is not a single scratch in my bed or on my truck. Just these three areas where the paint is flaking and showing rust. I only have 31,000 on the truck.
I still need to take it into the dealer for photos and approval from Toyota but there is a TSB on it according to the rep and my dealer.
2010 White CrewMax Rock Warrior