Akamai? Really. Either way, most of the ad revenue tends to come from the United States; the CDN is far from a requirement.
With a 1Gig connection you can only serve ~45 concurrents streaming 1080p. If you wanted to support more than 45 concurrents, you would need
1. To distribute content to separate instances
2. A routing infrastructure to reliably route connections to that content.
And then, congrats, you have just built your own CDN - albeit in one datacenter. If you don't want your users on the other side of the country constantly complaining that your site is slow compared to Vimeo, you would have to build it on the other side as well.
If you believe your hodgepodge CDN is going to be much cheaper than Cloudfront (on the order of 1 Euro/month, where you could support it on ~1.5M views/month), then you should probably skip the whole video sharing nonsense, and get rich becoming a CDN provider :)
If you believe otherwise, please enlighten me on how you can build a HD video streaming service for 100 concurrents without a CDN. Like I mentioned, on a 1GbE connection, you can serve a theoretical max of 45 users on one node. Where do you go from there without something that looks like CDN?