Apple tried to get these third party chargers "off the streets" by instituting an exchange program and also by educating consumers. But go into any pharmacy in the U.S. and you will see the Chinese made chargers, priced low enough to entice buyers.
Third party chargers can damage the U2 CI chip (circled) which is involved in recharging the battery
The problem is that the third party chargers do not regulate the charging mechanism inside the phone, leading to the release of excessive voltage that can damage the chips inside the device. Replacing a fried U2 IC chip can cost over $100, so next time you reach into the bin to pick out a cheap charger, remember that the money you save on purchasing the knockoff part won' be enough to cover repairing the damages caused by the third party charger. And of course, there is the chance that your life is in danger too. For a few bucks more, you can purchase the Apple certified part, keeping you and your phone safe.
source: Mendmyi via RedmondPie