As more and more personal device require USB charging, I have more charging plugs than wall outlet. They have USB holes that I can plug different cables for difference devices like iPhone, Android iPhone, netBook, digital camera, battery chargers, etc. If I look at the fine prints on each of the plugs, they all have the same volts, but different A output. All devices seem to be charging OK. But is there some harm to the device if I am not using the original plug?