That's Apple statistic, so I am a bit skeptical of it. That number is quite low for how big this story has become.
Even if it is a free market, there are things like implied warranties. Apple has obligations which it needs to live up too. If it doesn't, the end user will be angry.
I will believe Apple that they did proper testing when they designed these phones. I have no reason to doubt that they did. I bet the prototypes survived all the tests in real world conditions.
Nevertheless, I also believe that a small set of phones is failing (something around 1-2 percent). The most likely scenario is that there was a small batch of phones which were bending. Mostly likely due to either improper assembly at a single plant, bad materials being used etc.
Apple could have easily made the problem go away by replacing those phones. But Apple did not, as always the many 'Geniuses" at the Apple Store tried to find reasons not to replace the phone. That's the reason people are so angry.
That is a problem generally with Apple. With all their products, there is always a small batch which have manufacturing defects. Rather than recognizing the problem, Apple always goes out of their way to blame the end user or deny there even is a problem. If anything that makes a person less likely to buy Apple products in the future.
Consider this, a small chunk of Honda Civics from 2001-2005 have issues with ignition switches. The failure rate is probably in the 1-2 percent range. My 2002 Civic didn't suffer the issue however, that doesn't mean its not a problem. At the same time, the reason you probably never heard about it is that Honda promptly replaced the broken ignition switches.
http://www.startribune.com/business/100267579.html
If Apple could just adopt proper business edict and stand by their product even when it fails, then Apple would be criticized so often. Instead with Apple, you have a common problem, caused by a manufacturing defect, and Apple goes out of its way to deny there ever was a problem and blames the end user.