So much for putting your trust in cloud computing. T-Mobile’s Sidekick phones, whose storage of individual devices’ address books, multimedia, etc. on offsite servers was touted as a key selling point, have suffered a monumental outage that wiped out up to 1 million people’s phone data:

The phones are made by a Microsoft Corp. subsidiary and sold by T-Mobile USA, which say many Sidekick owners’ information is “almost certainly” gone… Microsoft spokeswoman Debbie Anderson said Monday that there was a still a chance some of the lost user data could be restored from a backup system. Engineers were working at it in the Microsoft data center where the failure occurred, she said.

The phones were troubled by a data outage a week ago. Service was intermittent last week, and then users started reporting that their Sidekicks were wiped of all personal information.

“This has been a terrible experience,” said Mary Boyle, of Silver Spring, Md. She lost more than 500 contacts, 100 pictures, a to-do list and dozens of Web site passwords. She also spent about eight hours on the phone with T-Mobile’s technical support last week, trying to deal with the outage, she said.

Yeah, yeah, everyone should back up their data, whether it’s on a phone or a computer. But not only do most people neglect this chore, the fact is that the Sidekick wasn’t designed to accommodate such an individual failsafe:

The Sidekick’s remote data storage feature was ahead of its time and served as a selling point for the device. It meant that if someone lost a phone, the contents could easily be downloaded to a new one. But the Sidekick didn’t complement the remote storage with a convenient way to save all data locally. Most newer phones, such as Apple Inc.’s iPhone, are designed to back up a user’s data when the device is connected to a PC.

Basically, it looks like if you own a Sidekick, and you’ve let the battery run all the way down, you’re out of luck. Quite a disintegration for the once hipper-than-thou phone-slash-accessory. It’s gone from Paris Hilton-endorsed coolness to tech toxicity.