Rackspace is changing its CDN partnership from Limelight to Akamai.
My book “Middleware and Cloud Computing” covering Rackspace Cloud and Cloud Files with the classical Limelight CDN as well as Amazon CloudFront gives a striking example of the importance of CDNs in modern system architecture. Often CDNs replace the front-end web servers for a cluster of application servers. Compared to offloading static content to web servers, CDNs are more scalable, provide lower latency for the clients because of the many cache locations and require no administration.
Many European companies that I know of are using Akamai already so moving to Rackspace Cloud becomes a much smaller step for them.