I live in the Boston area. Today, there were massive delays on the T trains (public transportation) all due to a power outage. The power outage which lasted about 7 minutes, was inadvertently caused by a maintenance crew accidentally tripping a breaker at one of the worst possible times – rush hour. To get everything back up and running took about 30 minutes, but the outage brought the trains to a standstill and things took awhile to get back to normal.
Imagine if someone did something similar to your IT infrastructure? This is why having clear processes, good plans, and fully testing everything BEFORE implementing in production is key.