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.
Customer safety is a top priority at Apple. That's why all our products - including USB power adapters for iPhone and iPad - undergo rigorous testing for safety and reliability and are designed to meet government safety standards around the world.
According to Apple's Takeback Program announcement, "Apple Retail and Apple Authorized Service Providers cannot advise you on the authenticity or safety of your adapter." They will simply replace any suspect USB power adapter with which you may have safety concerns.
Apple has also posted information on how to identify an Apple USB power adapter, but counterfeits can look amazingly similar, so when in doubt, replacement is advised. The green dot on Apple USB power adapters was added in 2008 to differentiate new products, after a recall for adapters sold with the iPhone 3G, as reported by MacRumors on September 19th, 2008.