Prior to the recent server move we were using ns1.webignition.net and ns2.webignition.net as DNS nameservers.
We moved to using ns1 to ns4.hostingreborn.com, which required everyone using ns1 and ns2.webignition.net to make changes to their domain names' records.
Whilst a bit of a hassle, I thought everyone could cope - after all, if someone can manage to set their domain's nameservers to ns1 and ns2.webignition.net, they'll be able to cope with changing them to ns1 to ns4.hostingreborn.com.
Well, some people can't, some people haven't and perhaps some people will forget.
So we've now set ns1.webignition.net to be an alias of ns1.hostingreborn.com and ns2.webignition.net to be an alias of ns2.hostingreborn.com.
So if you now can't or won't change your domain's nameserver records, you no longer need to.