I use this website all the time at work for material and finish specifications, if you want to know about anodising I suggest people have a little read:
http://www.matweb.com/reference/anodize.aspx
With some basic research it looks like a 6000 series aluminium will hard anodise to over the hardness of stainless steel, but any sharp internal or external corners will have weaker hardnesses and may chip. Have people only been experiencing these marks on the edges, or does it also chip on the faces?
If it's only soft anodising on the case then I would expect it to scratch and chip. It would be the same as any soft anodised product: keyring, torch casing.
The coating may also have been compromised by the manufacturing process. If the part has to be extremely thin but retain good rigidity then the type of aluminium they have selected to get these properties may not be suitable for anodising.
On a side note, I made my iPhone 3G last for over 3 years, I just took good care of it. Stop dropping your phones people! :rasp: