So now the missing Microsoft/T-Mobile Sidekick is back, doubtless relieving both hundreds of thousands of customers and the legal departments at the affected companies. But the questions about confidence in cloud-based data remain. And that's a good thing.While keeping mum about exactly how the missing customer data was recovered, Microsoft says the contact and other synced info is back in the Sidekick cloud.

All well and good, but the questions raised by the now temporary loss remain potent ones that every business doing business in or with the cloud (and that's most businesses, at least in some part) need to continue asking.

Chief among them is one addressed here yesterday: How confident should you be of cloud-based services?, but I think it's good advice.

It's not the least expensive advice, maintaining local backup in addition to, say, cloud based backup, particularly when part of the promise of the

No more confident than you are of any other technology, is my feeling.

These days that means pretty confident -- technology has tended to become more and more reliable, even as we ask more and more of it.

But the great risk of that confidence is complacency, whether the technology in question is the hard disk in your notebook or the cloud service that backs that hard disk up.

Things go wrong -- the Sidekick fiasco (shortlived or not) is the most dramatic of recent events, but Gmail and social networks have experienced outages and interruptions.

Likewise, that notebook disk can fail -- or the notebook can be stolen.

Point is, that the careful business (and consumer, for that matter) has a contingency plan in place should disaster strike. Backup your data regularly and don't keep the backup in the same place you keep the notebook.

The cloud requires a bit more wariness, I believe. Putting all your faith in a cloud-based service (even a cloud-based backup-and-restore service) and the ability of that service to restore all of its data (including yours) in the event of a massive failure is putting every one of your eggs in a remote basket in somebody else's henhouse.

I've hammered the suspenders and belt approach to data security before in various contexts , but I think it's good advice.

It's not the least expensive advice, admittedly. Particularly when part of the promise of cloud services the economy they offer, does it make sense to take on the cost in money and resources of a more local "just-in-case" backup?

Your budget will answer whether or not you can afford to have a really redundant backup strategy?

But while you're crunching the numbers ask another, equally or more important question:

Can you really afford not to?