Have you checked where the copper pipe came from and who made it. Not all copper pipe is alike. It is suppose to meet standards, but if you have extra lying around, you could get it tested. As far as well water you could gather a sample over a couple of days. One before house, and one from inside faucet. You can run a more thorough test on the samples. Also local water companies, I know of one in Washington DC who is doing a intense study on copper corrosion, erosion...
Also you may want to check if your pump is cavitating. That caused by not being far enough below water level (draw down level), or oversized for well. This will introduce an excessive amount of O2 into the water, causing high corrosion. This will also lead to premature pump failure.