My dns zone contains a loopback:
localhost IN A 127.0.0.1
Do I need it, and if so why? I can't think of a reason to have it here, especially as - without a dot - it would be
This answer on ServerFault explains what this localhost entry is for http://serverfault.com/questions/120769/localhost-in-a-dns-zone
It also talks about the possibility that such a DNS record could be use for Cross Site Scripting (XSS) attacks and suggest removing it for that reason.
Did your DNS undergo testing because a many times loopback entry tests ability to process Web requests without actually sending any messages out. I believe it is not needed.