At the APNIC meeting in Christchurch last week Sam Sargeant gave a nice talk on this. See http://www.apnic.net/meetings/26/program/apops/ for his slides. Leo Vegoda from ICANN pointed to this tool: http://recursive.iana.org/ which would be an interesting one for service providers to point out to their customers (unless of course they run the DNS for them and their servers are not right). A number of organisations in New Zealand have still not upgraded their software and many more are running servers that are recursive and authoritive at the same time. Time to get with the program!