Tears on both ends here, slowly but surely over the half year since new. The way the cable connects to the plug on the end of my friend's iPhone looks different to how mine was connected, which makes me suspect that they were making cruddy cables for a while.
I have heaps of cables that survive much better than this, including ones that get more used than my iPhone cable. I'm a traveling computer technician, carry my notebook and power adapter (usb HDD, usb mouse, etc...) around with me (1.5 years with no problem), but my iPhone cable usually sits in my computer at home, with no particular stress on it (0.5 years, torn).
With a bit of luck my retailer will help me out, but I'm not holding my breath - Optus Shop were hopeless last time, I'm sure they'll be just as "helpful" this time