Twitter outage via DNS hijacking showed another case of common symptom: DNS operation is simply neglected by people doing business on the Internet.
I was doing research on DNS transport security from 2002 to 2008. One of the reason I quit focusing on the research was that most, if not all, of the DNS problems are caused by operation failures, not necessarily due to technical deficiency of the DNS protocols and systems. In short, it's too political and social to do the technological experiments over DNS.
I still think DNS transport protocol issues are critical for stable Internet operation. But solving those issues does not help recovering human errors, such as lame delegation (missing link) between the domain name hierarchy. And stable operation of DNS systems is very difficult to maintain without stable hardware, software, networks, and operators.
I notice many small companies (especially in Japan) keep their authoritative servers inside their office, which is not good from the stability point of view. Actually, for many small Internet sites, including mine, not so many DNS zone records have to be exposed to the public. So I've already outsourced the DNS authoritative servers, while I periodically watch whether those servers do the right thing.
DNS is by definition a distributed system; and the management standard is much lower than what people (and even Internet engineers) believe. For the further details of how DNS is not well-managed, I suggest you to read a more detailed commentary on how important DNS is as an asset, by Danny McPherson of Arbor Networks.