I worked at Amazon on a team that built a mobile point of sale application. We had one supplier for our card reader that was this family owned company. It was a super tight night company — They even had a wall of how long employees worked at the company and some were there over 40 years. That being said, we (Amazon) wanted to move to blue tooth card readers. What I heard is that we tried to strong arm them into doing what we wanted even though the company had so many other clients and we weren't a big enough priority for them to drop everything and focus on us. The relationship was so strained that when myself and a few engineers went down to debug something with the hardware team from the other company, we were told to walk on egg shells and be careful about what we said.