Messing with DNS is doing it the Wrong Way. All of these CDN services are based on HTTP. When you're using them, that's an HTTP server you're talking to. It's perfectly capable of geolocating you by IP, and it can either hand you back links to a local CDN, or redirect you to another server.
Why the hell must we mess with DNS to do this? This is a solution which only works if you use Google DNS, OpenDNS, or sometimes if you use your local ISP's DNS. What if you're just running bind for you local net vs the root servers? Bzzt. Doesn't work.
The most insane thing about this is it's Google we're talking about here. They damn well know how to implement this entirely in their servers without resorting to DNS hacks. Why are they promoting this net-neutrality breaking, layering violating botch? We need less people to use this, not more.