I had a profitable Amazon store in 2010. I found niche products that Amazon didn't sell. As soon as I started getting traction on any one product, Amazon would start undercutting me, and my sales would drop to almost zero over the course of a couple of weeks.
I had near 100% feedback and I had a single customer complaint that I sold them the wrong product. Within a few minutes of me receiving this claim, my account was suspended. I had no chance to rectify the situation.
No amount of calling or emailing Amazon could get me in front of someone that could help me. All responses were an automated rejection.
This was a rough time for me as it was my only form of income and Amazon held almost $30,000 of my money for 3 months. I ended up having to close my business and move on, though I did eventually get all of my money back.
I've built multiple successful businesses since then and Amazon has recently had many business reps try to get me to sign up with a business account, because we purchase lots of items on Amazon/month. I always try to get them to re-investigate my old seller account and our email correspondence stops shortly after this. It's crazy to me that after 10 years and in a completely different industry, I still can't open a seller account.
It taught me a valuable lesson not to build my entire business on someone else's platform.
It only gives them more control over you and they will most likely use your customers, data, and more resources to out-compete you, if you get too big. Twitter has also done this to their app developers.
My wife runs a small business on Etsy and it's just as bad. They make random code changes, which bumps listings up or down and you suddenly have no orders for weeks at a time.
What's even scarier is if a handful of companies run everything we use online. Will I suddenly not be able to get a home loan for a decade because of an account closure?