Yeah, I also have an '05. Also, just rolled 30k and also just noticed some rust forming on the inside of my rear bumper. The outside appears to be fine, but up inside it's starting to look pretty ugly! It seems to be a bit early in the game to be thinking about rust. Especially since I am super concious of hosing out the underside of the truck every time I wash it just to make sure there is no dirt trapping water near any metal.