Remember Scratchgate? The original iPod nano (circa 2005) had some serious scratching issues that eventually lead to a class-action lawsuit.
Apple has since changed the polycarbonate (most recently to glass) in its mobile gadgets to minimize scratching, but it's still a problem for many. A cottage industry of screen film makers has developed to cater to iOS device users concerned about scratches.
Apple is researching a new scratch-proof coating, presumably for its mobile devices, that would prevent scratches.
The U.S. Patent and Trademark office published new application filed by Apple for "Nitriding Stainless Steel for Consumer Electronic Products" that describes a new system that avoid scratches by placing a layer of nitride over a stainless steel exterior.
In addition to providing a durable, hard surface that is both scratch and impact resistant, the nitride layer allows for the natural surface color and texture of the underlying stainless steel to remain visible to the user... It is this natural surface color and texture of the stainless steel that adds to the aesthetically pleasing appearance of the consumer electronic product, thereby enhancing the user's overall experience.
Apple acquired LiquidMetal in August 2010 gaining the technology behind a new metallic/glass substance that has twice the strength of Titanium but that can be molded like plastics. I wouldn't be surprised if the iPhone 5 was housed in a nitride-coated LiquidMetal.
Do you use a screen film on your iOS device? Why?