Ask HN: User authentication with AWS JavaScript SDK?

So Amazon AWS released Javascript SDK that can be used directly in the client side browser to use their services, without the need for a server to make the calls. If this is the case, is it possible to create a user, authenticate the user, and show content based on the login status? What services can you use for this? SimpleDB? RDS? S3 even? If this is possible, then it would mean that you can scale up without having to scale the server middleman between the client and Amazon. Are there any tutorials on this or a sample code which can let a user create an account, login, and access data from Amazon?