Passing startup script to Amazon AMI image using Alestic goodies

Alestic.com images allow you to run a startup script that is passes as a parameter to ec2-run-instance.
Fantastic. This couple with the handly runurl command (also from Alestic) allows me to nominate which S3-hosted Java JAR to run.
Allowing me the flexibiility to run mutliple different versions of a java-based runtime on top of a base AMI image.

Wait a minute... isn't multiple-runtime version support something that goes away when you move to the cloud... sadly not always.