Last week, users of T-Mobile's Sidekick smart phone—which is built and controlled by Microsoft subsidiary Danger—suffered a massive data outage that lasted for several days. This kind of disconnectivity would be notable in its own right, but now Microsoft and T-Mobile say that any data loss that customers experienced during the outage could, in fact, be permanent.

"Personal information stored on your device—such as contacts, calendar entries, to-do lists or photos—that is no longer on your Sidekick almost certainly has been lost as a result of a server failure at Microsoft/Danger," a T-Mobile/Microsoft statement to customers reads. "Our teams continue to work around-the-clock in hopes of discovering some way to recover this information. However, the likelihood of a successful outcome is extremely low. As such, we wanted to share this news with you and offer some tips and suggestions to help you rebuild your personal content."

Although the relative number of affected users is low, this incident comes at a tough time for Microsoft, which is busy pushing into the cloud computing market, where it's expected that users will store personal and professional information on web-hosted servers instead of local PCs and devices. That Microsoft was unable to protect user data in such a scenario is deplorable.

Keep in mind, however, that Microsoft inherited the Sidekick platform when it purchased Danger. The software giant will launch its own cloud-based OS, Windows Azure, next month. Windows Azure and Microsoft's other online services are based on a completely different infrastructure than is T-Mobile Sidekick.

Microsoft and T-Mobile say that they'll provide a new update today. I'm currently traveling home from Europe, so I'll provide an update on this information when I return.