I wrote this post ages ago, and therefore the information will sound a bit outdated, even if still accurate.
Prelude DNS is the service on which Internet is based, however, quite strangely it is often overlooked.
In order to provide the best possible reliability, a lot of energy is placed on the hosting. All major e-commerce sites are load-balanced with redundant database back-ends, etc.
Without a resilient and reliable DNS server, no one can hope to smoothly run any Internet services.