I'm aware of "round robin DNS" load balancing, but how can a single IP address be load balanced?
Google's DNS servers for example,
220.127.116.11. Wikipedia's load balancing article states:
For Internet services, the load balancer is usually a software program that is listening on the port where external clients connect to access services. The load balancer forwards requests to one of the "backend" servers, which usually replies to the load balancer.
..which seems reasonable when used with round robin DNS, however for the likes of Google's DNS servers this doesn't seem like a very redundant or capable setup.