There's something wrong with the anodizing processes if there is:
Discolouration and fading
A surface that its easily scratched
Anodizing is a process which 'grows' an oxide layer on top of the metal surface, the anodized layer provides protection for the metal finish and prevents corrosion when the surface is exposed to conditions which would normally result in damage to the underlying metal. When examined under a scanning electron microscope the surface is far from flat, it has pits in it, which in a thin layer anodising process could reach the metal below.
Black dye is applied to the anodized surface during the treatment process, its not a paint, it is a colour absorbed into the anodized layer, black anodizing is not easy to achieve, often coming out a very dark brown.
Not all anodizing is equal, it all depends on the effort (=time and cost) put into the anodizing process, you can have thin (5 micron) up to thick (30 micron and thicker), thin isn't particularly effective at resisting scuffs and scratches, a thick hard anodized coating (because hard anodizing is a different physical process from normal anodizing) is effective at resisting key scuffs and grains of sand etc, it all depends upon the conditions, drop your iP5 onto any non soft surface and its likely to suffer some damage.
From the complaints and pictures I have seen, Apple has a quality control problem in manufacturing of the back panels, assembly, and final inspection - probably all driven by the need to get millions of phones out to customers with a very short manufacturing lead time prior to 21st September - no phone should be coming out of the packaging with dings, dents and scrapes or scuffs, aluminium is easily damaged in transit, especially if the finish required is near perfect (such as a mirror finish) so we used to paper wrap each length prior to shipping, naturally the customer paid for such care in handling, packing etc in the price they paid.
If the colour on an iP5 scratches off - its paint, not anodized, anodizing never produces a gloss finish and takes a lot of effort to scuff and scratch.
Why do I know this?- a BSc. degree in Metallurgy and Materials Science and a year in an Aluminium Extrusion plant... but I confess to checking a few details from http://en.wikipedia.org/wiki/Anodising as its over 30 years since I graduated and the little grey cells were a bit vague on quite how deep the anodised coating could be.