A big selling point for cloud computing is resilience. That is, the cloud shouldn't break, at least not very easily, as it's hosted in multiple data centres with back up power, separate network connections and knowledgeable techies on call 24/7 in case something happens.
The truth is however that the cloud can and will break, as happened this week when Amazon Web Services in Sydney went offline partially. Power was lost at one the cloud giant's data centres during the massive storm that hit the city, which in turn took out lots of online businesses. It took six hours before AWS was back to normal. Big names such as Domain, Carsales, The Iconic, streaming video company Stan and Domino's Pizza that depend on the internet for their business were inaccessible.
For an online business, six hours of problems must seem like an eternity. More so because there's not a huge amount admins can do, besides trying to connect to the cloud provider and attempt to start up their site services.
Outages, however, are something any cloud-based business must factor in, because one day that remote data centre somewhere will be unreachable, with potentially disastrous financial effects.