This is a neat article, but 'CDN' is such a broad term. This is much more a very well done proof of concept article, but fails to take into account the huge scope of a large scale CDN, and all associated quirks it comes with.
They also account for an infinitesimally small amount of global net traffic. Their rapid adoption of IPv6 is more symbolic than anything else. And it got them mentioned here, so presumably it was a success.
Major CDNs do use anycast routing, in conjunction with DNS/geolocation based routing in locations where anycast's results would be unpredictable (usually in locations where there are many POPs.)
If the deal goes through, it may require Facebook to take a different approach with their CDN strategy. They will probably either begin to roll their own (given their size and budgets), or move to a blended environment where they utilize multiple CDNs based on region and traffic levels.
For example, Apple historically has used Akamai for their content delivery, but as of around ~2009, they began to use Limelight in conjunction with Akamai. Just today with the iOS 5/OS X updates, I noticed at home in Los Angeles that the delivery from Limelight was terrible. I tried it again about an hour after release, and I was then being sent to Level3.
Akamai's footprint exceeds 100k servers worldwide now, and that's just what they publicly disclose. It is likely more if you count in their DoD contracts. They're probably on par with Google now.
