On Saturday, T-Mobile and Danger issued a statement to their customers, warning that the data "that is no longer on your Sidekick almost certainly has been lost as a result of a server failure at Microsoft/Danger."

Bad news, T-Mobile Sidekick owners: your data may be gone for good.

Last Monday, when their Danger Sidekick devices lost data services, losing access to their address books, calendars, and other services which Danger owner Microsoft had stored in the cloud.

On Saturday, T-Mobile and Danger issued a statement to their customers, warning that the data "that is no longer on your Sidekick almost certainly has been lost as a result of a server failure at Microsoft/Danger."

"That said, our teams continue to work around-the-clock in hopes of discovering some way to recover this information," the two companies added. "However, the likelihood of a successful outcome is extremely low."

Although Danger is owned by Microsoft, a proponent of cloud-based computing, where data is stored and possibly reproduced across a number of services, apparently only one server was used. The loss is undoubtedly more acute for Danger, which touted the server-based model as one that promised an advantage over its competitors.

"Our architecture shifts heavy processing tasks to our server instead of client devces [sic], creating the power and economic advantage of the Danger solution," Danger claims. "The system components work together to provision and manage all user services and user data, and allows our developer community to create premier mobile content."

The two companies strongly recommended that users not totally discharge the Sidekick battery or remove it, as that would eliminate the address book and other stored data from the Sidekick's memory. "We continue to advise customers to NOT reset their device by removing the battery or letting their battery drain completely, as any personal content that currently resides on your device will be lost," the Danger/T-Mobile statement said.

But one of the proposed solutions in the linked FAQ to restore contacts suggests doing just that, removing the battery and placing it in another T-Mobile device, to try and save contacts to the SIM. Other suggestions include emailing contacts from Outlook or Gmail in vCard format.

T-Mobile had already begun promising customers who had been hit by the outage a month of free data service. T-Mobile also implied that more compensation would be coming soon: "We also are considering additional measures for those of you who have lost your content to help reinforce how valuable you are as a T-Mobile customer," the company said.