Microsoft Azure, Nov. 18
We don't want to seem like we're beating up on Microsoft here with its fourth appearance on this list (including its role in causing the No-IP outages), but Microsoft's stature in the industry certainly warrants the scrutiny.
And as Gartner Distinguished Analyst Lydia Leong complained after this crash in November, "Microsoft's disastrous inability to keep Azure outages confined to a single region is a major red flag for enterprises considering Azure."
The Nov. 18 outage that affected customers around the world using a variety of Azure services was caused by a glitch in a performance update to its cloud storage service.
Microsoft ultimately determined human error was the culprit.