In mid-2012, Apple was heavily criticized for its warranty policies in China (1, 2, 3). There, among other things, she was accused of using used or reconditioned parts to repair defective devices, in addition to not returning the exchanged components to the consumer.
Through a statement (Google Translate) on the company's Chinese website, CEO Tim Cook apologized and announced that Apple will implement some changes to the warranty policy as of this month. Among them, the repair policy for iPhones 4 / 4S and Macs (replacing old parts with new and non-refurbished parts), increasing the supervision and training of authorized assistance, in addition to improving the information about warranties posted on the company website and contact for consumer feedback.
iPads and iPods touch are out of this list of repairs because, in their cases, Apple usually exchanges them for new devices, since it is very complicated to fix these iGadgets.