When I was first looking at aws, I received a billing prediction alert that was ridiculous high. I could not find the culprit (I only had an ec2 instance and some other random services I looked into). In the end I deleted my account, to avoid this unexplainable billing. Next day, I got an email saying I erroneously got the alert. Damage was already done, but at that time, I was only exploring what the cloud had to offer, so no real damage done.... until a couple years later when I had to do some real aws for my work. Because I deleted/disabled my account, I cannot reopen an account with the same email address.