People often mix and match anycast/Geo DNS and anycast/unicast http.
Some even go a step further and, for video files, anycast to a node that 302s to it's own unicast address.
Right way: 1-2 major Tier1 carriers across all of your PoPs with local peering for regional eyeball networks.
Wrong way: Using a different set of transit carriers at each location.
You really don't want that many AS paths to reach your content from a given location (3-4 is more than enough). What you're really going for with BGP anycasting is that your local ISP has a direct route to the closest PoP via exchange peering, or that the Tier1 path drop you off to the "closest" route. Transit carriers do this for a living, and they're usually quite good at figuring out route weighting inside their own network.
Yes, I know Netflix does it differently but they use a lot more smart geo DNS routing than anycasting.
Edit: IMHO it's also better to choose a Tier1 with a moderate sized network that values stability and performance over size. So someone like NTT over say Level3.