T-Mobile Sidekick owners last week were reminded about the risks of relying too heavily on cloud computing when a massive failure at Microsoft's Danger subsidiary left the handheld owners without access to the Web or their address book for several days.

If that weren't bad enough, after some of the data had been recovered, Microsoft on Saturday told customers that any other missing data may be permanently lost. While it's not uncommon for outages to occur, the potential for permanently lost data casts a dark cloud over, er, cloud computing.

For Microsoft, the timing couldn't be any worse. Next month, the software giant will launch Windows Azure, an operating system in the cloud. Microsoft is quick to point out that the Azure service is built with redundancy in mind and is able to withstand failures in single or multiple nodes, but will that be enough to convince users to put their confidence in the cloud?

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