Article says: "Secondly, Virtual DNS masks the true origin IP addresses of the provider's nameservers behind CloudFlare’s IP addresses. Visitors and/or attackers only see CloudFlare’s IP addresses when requesting answers, keeping customer nameservers safe from being targeted by attackers."

If I sign up for this service, do I get a list of Cloudflare IPs so I can firewall everybody else off? Otherwise this is mostly security through obscurity. Nameserver names are often easily guessable (ns1.example.com, ns2.example.com, ...).