I agree that battery replacement is dangerous - I have ordered several replacement batteries for my Note 2 from ebay. They all had Samsung labeling, but exhibited wildly erratic discharge (dropping from 50% to 10% within a few minutes).
I have since replaced them with Anker batteries, which appear to have a good reputation for quality and safety, and are really not much more expensive than the Chinese low-end. People should be encouraged to avoid batteries made in China for safety reasons, unless they are vetted or supplied by an OEM.
The chargers also can be dangerous, and low-end Chinese manufacturers skimp on safety and quality. Look for the "UL" symbol for Underwriters Laboratories on any USB chargers. Also check for spelling and grammar mistakes in the labeling on the device, which are sure signs of a cheap forgery.
Power components must be purchased from reputable suppliers to assure safety.