Cloud computing may be significantly changing the way many companies do business on the internet, but it isn’t perfect.

As we’ve seen time and time again, the cloud infrastructure can fail, leaving users which made poor architectural decisions in a bind. There are also security and financial concerns that the cloud raises, some of which companies fail to deal with intelligently.

The fact that cloud failures are often the result of poor decision-making on the part of companies using the cloud doesn’t of course negate the fact that when the cloud causes problems, it can be painful. And painful is how to best describe what many Microsoft Azure customers are feeling right now.

As reported by The Register, Microsoft’s cloud platform, Azure, experienced an outage earlier affecting its service management system. As a result, some customers were unable to execute “service management operations” for some 8-plus hours. In other words, they weren’t able to control their cloud computing resources. As one Azure customer told The Register, this created an “admin nightmare.”

Microsoft finally identified the cause of the problem — a “cert issue” — and started rolling out a hotfix. That is obviously good news for Azure customers who have been waiting eagerly for a resolution to this matter, but the fact that such a vital part of the Azure platform went down is sure to create long-lasting concern.

As one Azure customer who spoke to The Register put it, “This should never happen. The system should be redundant and outages should be confined to some data centres only.” To which the response should be: famous last words.

If there’s one thing we’ve learned about the cloud, it’s this: it can and will fail in unexpected ways. Customers of cloud providers should therefore make no assumptions about what can and can’t happen. Operating infrastructure is difficult, which is why so many choose to leave that to cloud providers like Microsoft and Amazon. But in doing so, they effectively put their applications into a big black box that they can’t control.

Sensible? Despite the potential pitfalls, there’s a strong argument to be made that for some companies cloud computing is the right choice. But the companies that want to weather the worst storms will need to be a little more paranoid about worst case scenarios.