What a gang of morons, they really do show the lack of knowledge. Let me explain
There are not 13 root servers ( as discussed in that ridiculous article ) What there are is there are many hundreds of root servers at over jizz load of physical locations in many countries. There are twelve orgs responsible for the overall coordination of the management of these servers.
There is a technical design limitation that means thirteen is a practical maximum to the number of named auths in the delegation data for the root zone. These named auths are listed alphabetically, from a.root-servers.net through m.root-servers.net. Each has associated with it an IP address (and shortly some will have more than one as IPv6 is further rolled out).
Anycasting, diversity,fat pipes & gTLD servers which only resolve the last part of names like .com or co.uk and it passes that request to gtld servers, that they practically have no use. Also, the caching..
