Now that most registrars allow nameserver records to be created that have the same IP address as a previously registered nameserver (this was not allowed before as far as I know).

Is there any reason to pay extra to get a unique IP address from my host to point my nameserver entrys at or should I just do the dual mapping of them onto the hosts existing dns servers. Does this breach any RFC or have any technical drawbacks?

If you have two nameservers, ideally located at two different locations and on different subnets, it would provide redundancy and better performance.

Having two addresses on the same server would provide no benefits, because if the server went down both of them would be unreachable.

Originally posted by lewney
...because if the server went down both of them would be unreachable.

A lot of "smaller" sites only have one server -- if my one and only server goes down, it doesn't matter if people can get DNS info or not.

Of course, a large company would have multiple servers, in which case your comment is definitely important. :)