I was also expecting amazing optimization tricks, like:

- Designing an MPEG encoder which can take a couple of pictures and render them on the fly, so only saving the pictures,

- Carefully spreading the views over a period of time,

- Associating the soundtrack at view time, since the soundtrack is the same for everyone,

- Using EC2 for the purpose, deleting all vids afterwards,

But no, they just used the brute force method.

It would be a good job interview question: "How would you serve 700m videos?"