Object Versioning - Why It's Good for You
The new function is pretty easy to understand. When an existing file is uploaded to S3, instead of overwriting the original, the service will create a new revision. This means you don't worry about accidental deletion, overwriting a good file with a corrupt one, and using S3 for backups looks like it'll be much easier.
Object Versioning joins S3's gang of other features, including Backups, Content Distribution and File Sharing.
Why It's Good for Amazon
By adding the feature, Amazon is providing what people have already come to expect thanks to similar services like DrobBox (which uses S3 for storage).
Moreover, with Amazon you pay for what you use. Each time a new version is created, more space in the database is taken up. The more versions created, the more expensive the service becomes for the user and the more money Amazon gets in their pocket.
Why It's Good for Others
The addition mixes well with third-party solutions as well, such as offerings from CloudBerry Lab. Their tool, which previously assisted with Amazon S3 backups, allows users to preserve, retrieve, and restore any and all versions of documents in an Amazon S3 bucket.
The new version of CloudBerry Explorer (v1.8) turns on versioning aware mode across all Amazon S3 regions, or just specific buckets, and performs common file operations on object versions as well as recover accidentally deleted objects.
Currently, Amazon's Object Versioning is in beta. For an overview of what else Amazon S3 has to offer (and pricing plans), check out their site here.