So I was noodling around with Amazon EC2 a few days ago. I used one of their quick start Linux machine images for about 10 minutes, then terminated the instance. Afterwards, I noticed I had some EBS volumes that were terminating also.
This is a complete noob lesson, but some AMIs use EBS volumes for their root disk instead of loading from S3. Thus the unexpected EBS volume. Operator error, please read the fine print.
It’s not a huge deal, although you could inadvertently incur costs with an EBS volume, since they’re metered by I/O operations in addition to storage. I’m assuming Amazon pays for the storage on these volumes but the user forks over for the ops.