MNAME not a listed NS record

[Dave Warren]

Is there anything technically wrong with having a SOA MNAME field that 
isn't listed as a NS record?

The server listed as MNAME will host the zone and is authoritative for 
the zone, but out of latency concerns it isn't ideal to have other 
resolvers querying this server.

Various online DNS diagnostic tools throw warnings, but as far as I can 
tell from the RFCs, this is a valid configuration. Is it valid? Are 
there any operational gotchas to be aware of or can I ignore the "warnings"?

-- 
Dave Warren
http://www.hireahit.com/
http://ca.linkedin.com/in/davejwarren