Looks like RackSpace is doing DNS as a service with an API. Here are the links:
Retail Site
http://www.rackspace.com/cloud/cloud_hosting_products/dns/
API Developers Guide
http://docs.rackspace.com/api/
Tutorial
http://www.collazo.ws/2011/07/08/using-rackspace-dnsaas-with-curl-part-1
This should make it much easier to do bulk DNS operations in the cloud.
