Comment 1 for bug 437877

Addendum... since there's already a hook for DNS control, perhaps a generic interface to allow multiple methods would be the way to go.

For the EC2 elastic IPs, apparently
 - it's classified as "out-of-datacentre" traffic and thus charged.
 - it's slightly slower, leading me to believe they might proxy it rather than assigning the IP to an instance.

Another method is to not use DNS but /etc/hosts and update it at high frequency.
With a generic interface we can add a few methods to choose from as appropriate.