Because with a low DNS TTL and you get a DDOS attack like what happened at DNSmadeeasy, your sites go down in 5 minutes. Also a high TTL puts lower load on the

Because with a low DNS TTL and you get a DDOS attack like what happened at DNSmadeeasy, your sites go down in 5 minutes. Also a high TTL puts lower load on the DNS servers and increases response times. All that being said, I still use a low TTL so that I can quickly switch servers in the event one goes down.