Amazon EC2 Makes AMI Tag Sharing Effortless Across Accounts
Amazon EC2 now lets you share selected tags with all accounts that receive your AMIs—just prefix tags with 'ec2:SharedTag/' and they automatically sync everywhere. This kills the need for custom tag replication scripts, keeps shared tags read-only for recipients, and rolls out to all AWS Regions at zero extra cost.
source: [aws/whats-new]