This takes a rather narrow view at what is DNS. For DNS as a service to work, it has to be accessible and give the right answers. It doesn't matter why it is n

This takes a rather narrow view at what is DNS. For DNS as a service to work, it has to be accessible and give the right answers. It doesn't matter why it is not accessible or why it doesn't give the right answers. If it doesn't, then the service is broken. DNS is in the unique position that it is relatively high up in the network stack, so lots of (network) failures affect DNS as a service. It is a big distributed database, which gives many possibilities for wrong data, it is used by almost all applications, so a failure of DNS as a service is highly noticeable. Finally, DNS has by nature (some what) centralized choke points. If you have a domain like company.com, then just about everything that company does has to go through the DNS servers for company.com. Any small failure there can have a huge effect. So DNS is a pretty exciting field to work in.