Given that storing static content is the main use case for Amazon S3 service and considering the fact that many large players rely on CDN to scale distribution of such content, I want to know whether Amazon S3 provides some sort of CDN functionality? I can easily imagine them storing multiple copies of content for fault tolerance/scalability, but does that put it on par with CDNs? If not, why not?
From What Is Amazon CloudFront?:
Amazon CloudFront is a web service that speeds up distribution of your static and dynamic web content, such as .html, .css, .js, and image files, to your users. CloudFront delivers your content through a worldwide network of data centers called edge locations. When a user requests content that you're serving with CloudFront, the user is routed to the edge location that provides the lowest latency (time delay), so that content is delivered with the best possible performance.
You can decide to put Amazon CloudFront in front of your application. This will enable static content to be cached in edge locations around the world.