In a statement on Thursday, Amazon said an employee on its S3 team was working on an issue with the billing system and meant to take a small number of servers offline -- but they incorrectly entered the command and removed a much larger set of servers.
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According to Synergy Research Group, AWS owns 40% of the cloud services market, meaning it's responsible for the operability of large swaths of popular websites.
http://money.cnn.com/2017/03/02/technology/amazon-s3-outage-human-error/