Amazon S3 now supports versioning on objects. This means you can send new versions of objects to S3 and they persist older verions. The version numbers are arbitraty strings, so semantic versioning would work just fine. Potentially you could have a client application that allows you to store private npm packages on s3. If the package 404s, then you can fallback to the main npm registry. This is effectively a quick and dirty private npm.
My question is, what am I missing? Is there more to npm that versioned s3 objects can provide?