A blued surface is no magic bullet -- just look at some old Winchesters and you'll observe that the rust patterns do not necessarily have anything to do with wear or surface damage. When there is a scratch it is usually a rust point, yes, but then there's also the freckle rust pattern that is pretty much random (where ever moisture condensed onto the surface). The reason is that the blue oxide is only metastable, and it doesn't take much environmental change for it to revert to red oxide.
Modern nitride finishes are about as close as you can get to rust proofing steel without plating.
The misconception about this polishing chestnut is that reducing surface area reduces it's tendency to rust - what it does is minimize the area exposed to oxygen. The surface will still rust at the same rate as a smaller part that has the same surface area under the same conditions. The effect is proportional to the reduction in area - ie, very small.
