The thing to note is that implementation of browser prefetching is further putting DNS requests out of the control of the publishers. 10 billion queries was something like 5000 dns req/s and that is considerable resources of some dns service. I wish dns was not per query costs, but it would seem that is the metric that resources would be based on. The point of the article is to let people know that if you fall into this dns pattern, it maybe a result of the recent prefetching done by browsers, and you may have a way to resolve the issue.