It is using Amazon's Cloud Services:
Amazon.com, Inc.
Amazon Web Services, Elastic Compute Cloud, EC2
1200 12th Avenue South
Seattle
98144
USA
via:
Akamai International, BV
They have a premium streaming service too. If you stream a video and stop it part way through, you can continue playing it at any time, even days later. It maintains the connection.
That doesn't happen on YouTube for example. After some number of minutes they drop your connection and you have to refresh the page to remake the connection to continue streaming.