First, Amazon killed off most physical book stores. Now, there’s not much competition remaining and they begin to open their own stores.
I experienced market dominance first-hand when one retailer completely controlled my local market. 12 years ago, the biggest bookstore chain in Thailand took over the second biggest bookstore chain. They now had full control over the market and dictated which books would fail or succeed. Some of my personal best-selling books were discontinued for distribution, with no reason stated.
A company completely controlling a market can either make or break you. We as authors should not neglect the other book retailers (Apple, Google, B&N, Kobo).
What would happen if Amazon suddenly restricts your account?