AWS EBS outage, Fukushima, Chernobyl, even the great Chicago Fire (forgive me for comparing AWS to those events).
Sure there's always a "root" cause, but more importantly, it's the related events that keep adding up to make the failure even worse. I can only imagine how many minor failures happen world wide on a daily basis where there's only a root cause and no further chain of events.
Once a system is sufficiently complex, I'm not sure it's possible to make it completely fault-tolerant. I'm starting to believe that there's always some chain of events which would lead to a massive failure. And the more complex a system is, the more "chains of failure" exist. It would also become increasingly difficult to plan around failures.
edit: The Logic of Failure is recommended to anyone wanted to know more about this subject: http://www.amazon.com/Logic-Failure-Recognizing-Avoiding-Sit...
„The genius of a construction lies in its simplicity. Everybody can build complicated things."
Also, a couple other complex systems for your trend are; financial markets and commercial jets.
The examples he draws from are nuclear power plant failures (TMI in particular), civil aviation and oil transport. But the basics will be recognizable to anyone who has dealt with large computing installations; interactive complexity, tight coupling and cascading failures.
It is not a reassuring book, you won't be able to look at any complex system without asking yourself what sequence of simple, predictable failures of widely separated parts could tip it into a catastrophic failure mode.