Comment by ocdnix

This doesn't cover other interesting uses, like tag-based automation. Random examples: Tagging DynamoDB tables to identify which should be backed up and at which frequency (when you don't quite trust the built-in backup); tagging dev RDS databases with a shut-down schedule for nights/week-ends; tagging Elastic IPs and Auto Scaling Groups with a "IP pool ID", and a Lambda that re-assigns EIPs to ASG instances as they are recycled; using a "data flow ID" tag on resources that are in the hot-path of data flows that are subject to high-volume bursts, so you can easily list them and scale them up before known events.