The creator of the first Ubuntu distros for EC2 wrote about the dangers of public EBS snapshots 10 years ago:

https://alestic.com/2009/09/ec2-public-ebs-danger/

He just got notified by AWS a couple days ago about the public snapshot he mentioned in the article.

But at least AWS is trying to make things better here by proactively checking for public EBS snapshots and notifying people.