Over 7.5 million websites use Cloudflare, and 3,280 of the world's10,000 most popular websites depend on its content delivery network (CDN) services. The good news is that the CDN didn't go down. The bad news is that Cloudflare Dashboard and its related application programming interfaces (API) were down for almost two days.
That kind of thing just doesn't happen -- or it shouldn't, anyway -- to major internet service companies. So, the multi-million-dollar question is: 'What happened?' The answer, according to Cloudflare CEO, Matthew Prince, was a power-related incident at a trio of the company's primary data centers in Oregon, which are managed by Flexential, that cascaded into one problem after another. Thirty-six hours later, Cloudflare was finally back to normal.
(as others have pointed out and CF has more or less acknowledged: three data centers in one small city can be expected to share their fates in many scenarios.)