Sure, but a lot of people use other people's DNS services. The number of times I've been allowed to build a DNS service for my employer is zero. I've used static DNS, where you just put in your X number of A records and hope; dynamic services where you put in X and have them serve only Y of them in any request and hope. I've used services with load feedback, but those are always a much higher tier.
>Sure, but a lot of people use other people's DNS services
There are many of DNS services which offer an API for querying and updating records.
It is very easy to write a service / script that just fines the X least loaded servers and then call an API to set those as the available records.
In practice you will also want to implement some monitoring that it is actually working.
