If you are used to setting permissions in Amazon buckets, you're probably familiar with S3's style of ACL usage appended to the source URLs. In Rackspace, no URL defined permissions exist. The way to set public versus private permissions is via containers.
Public: Select 'Publish to CDN' in the container properties. This creates a link that allows that particular location to be viewed by anyone. This is the only way to enable public viewing if your videos are stored on Rackspace's CloudFiles. Through this function, Rackspace simultaneously publishes your content to Akamai's CDN. No additional steps are required to enable this feature.
Private: With a valid username and API Access Key in the source or destination URL, you're allowing Encoding.com to use your credentials to access your content.