Amazon S3 API is simple and there is beauty in the simplicity. Google noticed and the Google Storage for Developers has almost same set of APIs. Eucalyptus has Amazon-S3 compatible API too. German based Dunkel Cloud Storage is in this group as well.
Most recently, Mezeo announced availability of Mezeo Interoperability API, compatible with Amazon S3, Google Storage and Eucalyptus.
So what is so valuable in the Amazon S3 API that it is becoming a standard?
The biggest benefit is the number of applications and tools that supports Amazon s3. Amazon S3 arrived in this cloud storage marketplace early and it has built up a significant developer base that are familiar with Amazon S3 and supports Amazon S3. Supporting Amazon S3 API means the newer cloud storage vendor can immediately tap into this huge S3 developer base and catch up sooner.
The second benefit is that the API is quite simple, buckets and blobs and a few operations on them. So it is fairly easy to follow.
Microsoft has a different approach in its Azure Blob Storage. The API is similar but different enough to say it is not a clone. Especially when it comes to page blobs and block blobs in Azure.
We have seen the Netscape vs. IE and other wars Microsoft fought before.
Is it going to be an API war between Amazon S3 camp and the Windows Azure Storage camp?