That is not exactly true. While Amazon IS heavily customer service oriented, and WILL get rid of sellers that do not meet the performance standards, they actually have people to evaluate these things.
Foe example, let's say you sells DVD's on Amazon - one of the MOST DIFFICULT categories to survive in. You have 9 positive ffedbacks, but number to is a 1 star negative. It reads "Seller charged $2.98 for shipping, but the label says it only cost $2.07 - FRAUD!!!"
That will NOT get your account cancelled.
On the other hand, if it were to read "SOLD BOOTLEG COPY! AVOID SELLER!". That is MUCH MORE LIKELY to cause you to lose your account.
And if it read "DVD skipped in parts and was nearly unplayable." then it could go either way. They would look at what titles you were selling, your sales volume, and whatever their internal risk models are.
Sometimes you can have 100% positive feedback and no claims or complaints and lose your account. For example, a customer calls Amazon directly and advises them that you sold them a box set of DVD's - and the packaging contained misspellings and the UPC code was wrong. THAT will cause you to lose your account.
Amazon can be harsh, but it is not true that any new seller that receives even one single negative or complaint will lose their account. It depends on the circumstances.
Once you have a selling history and many feedbacks (you mentioned 200) then they tend to follow percentages more closely. But even if you have 200 positives, if they think you are selling counterfeit merchandise, your account will be gone.
This is just one example and there are many variables in each case. Slow shipping, poor communication, bad customer service, low quality merchandise - all of these should be avoided.
But other than being rude with customers or selling counterfeit merchandise, you can usually reason with Amazon. Not always, but most of the time.
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