In 2004, Jeff Bezos and his technical adviser Colin Bryar drove together to the city of Tacoma, an hour south of Seattle in Washington State. At that time Amazon was a multi-billion dollar company. However they were headed to Amazon's customer services centre - where they were to spend two days as customer service agents. "Jeff was actually taking the calls himself", Bryar says. He recalls that a complaint on one product in particular kept coming in. "Jeff's eyes went wide," he says. Bezos was frustrated. There was clearly something wrong with the product, but it hadn't been escalated. Later that day he sent out an email asking for more efficient ways of flagging faulty products. Bezos steps down from Amazon on Monday - exactly 27 years after he founded it. In that time he has developed a series of unusual leadership principles - which some argue are the backbone of his success. Others believe they speak to everything that is wrong with Big Tech. Talk to anyone who's ever worked at Amazon, and you don't have to wait long before you hear the phrase "customer obsession". For Bezos, profit was a long-term aspiration. For a company to be successful it had to have happy customers - at almost any cost. Nadia Shouraboura started working for Amazon in 2004. She went on to be invited into the elite "S-team" of Amazon managers - the senior managerial board. But when she first started, she thought she was going to be immediately fired. "I made the biggest mistake of my life during our Christmas peak," she says. Shouraboura had ordered key products onto warehouse shelves that were too high. It would take time and money to get the right products off the shelves. "I came up with a clever way for us to lose as little money as possible, and sort of fix the problem. But when I talked to Jeff about it he looked at me and said, 'you're thinking about this all wrong'. "You're thinking how to optimise money here. Fix the problem for customers, and then come back to me in a few weeks and tell me the cost."