Recently two major cloud computing services, Amazon's Elastic Compute Cloud and Sony's PlayStation Network, have suffered extended outages. Though the circumstances of each were different, details that the companies have released about their causes show how delicate complex cloud systems can be.

Cloud computing services have grown in popularity over the past few years; they're flexible, and often less expensive than owning physical systems and software. Amazon's service attracts business customers who want the power of a modern, distributed system without having to build and maintain the infrastructure themselves. The PlayStation Network offers an enhanced experience for gamers, such as multi-player gameplay or an easy way to find and download new titles. But the outages illustrate how customers are at the mercy of the cloud provider, both in terms of fixing the problem, and in terms of finding out what went wrong.

The Elastic Compute Cloud—one of Amazon's most popular Web services—was down from Thursday, April 21, to Sunday, April 24. Popular among startups, the service is used by Foursquare, Quora, Reddit, and others. Users can rent virtual computing resources and scale up or down as their needs fluctuate.