Apple will initiate a USB Power Adapter Takeback Program on August 16, 2013 in response to recent safety issues with some counterfeit USB power adapters for iOS devices.
To qualify for a new specially-priced US$10 Apple USB power adapter, you must bring your third-party adapter and your iPhone, iPad, or iPod to an Apple Retail Store or an Apple Authorized Service Provider. The retailers will validate the serial numbers and you can buy one adapter for each iOS device you bring in until October 18, 2013. Not all Apple Authorized Service Providers may be participating in the buyback program, so check Apple's site for potential locations.