Even better is the fact that they have absolutely no support for marketplace sellers. If you get your account banned by their automated system, the only thing you can do is email their tech support and get automated responses back.
They take a 16% cut of most orders. I made them thousands of dollars last year as a result of my sales and they couldn't even give me the common courtesy of being able to talk to a support rep when they banned my account. To this day, I still don't know why my account was banned. I've been selling for years on other venues with no issues.
I always have positive feedback and answer customer issues quickly.
Even worse is that when you're on Amazon, you pretty much have no control over your business.
You can't communicate with your customers outside of Amazon and if a customer makes any sort of claim (through their A-Z claim system), they win 99% of the time. As in, they didn't like the item for whatever reason, make a claim, and get a refund without you getting your item back.
I seriously doubt if you ordered an iPad on Amazon and wanted to return it that they would give you a refund before you actually returned it.
Oh and one more great thing I wanted to add: Although Amazon has a 30-day return policy, they will force you to give refunds even a year after a person ordered something from you. This happened to me and I know it's happened to other people.
I'm thoroughly disgusted with Amazon's business practices.