Sam Gustin asks: When will "Cloud Computing" be as reliable as your ATM?

In the last year, the idea of "cloud computing" -- the transition of desktop computing functions like email and word processing to external servers managed by tech giants -- has gained an enormous amount of traction. Today, most tech observers agree that in the future, much of our data will be stored in "the cloud," a vast network of inter-connected web-based servers far removed from individual users.

But several recent high-profile outages of popular web-based services, including Twitter, Amazon's S3 storage system, Apple's MobileMe web software suite, and now Google's Gmail, raise serious questions about the reliability of cloud computing. (After a 90-minute, apparently system-wide outage, Google said the problem was fixed.)

The GMail outage affected millions of users in the middle of Monday afternoon. Consumers and businesses weighing whether to use Google's online suite of tools, Google Docs, have taken notice. "Given the amount of my digital life that is stored at Google, it's a wake-up call," wrote Mashable.com blogger Mark 'Rizzn' Hopkins.

As it is, "cloud computing" requires a leap of faith. Its proponents, which include Google, Microsoft, and Apple, are basically asking users - and businesses - to entrust them with valuable data. But if these tech giants can't ensure the reliability of these services, why would anyone choose to use them?

Cloud computing proponents say they offer more space and better group productivity tools at a lower cost. Fair enough. If the service works.

In a way, these companies hope users will view their services the same way people commonly view banks: as a safe, reliable depository of valuable content that can be accessed at any time, through ATM machines.

But imagine if ATM machines failed the same way the services from Google, Apple, and Amazon have in recent weeks.

Venerable tech blogger Om Malik, who has been at the forefront of chronicling the recent troubles with web-based services, wrote that the Gmail outage brought his company to a halt.

"Given that our company relies on Google's Gmail and GTalk service, our operations came to a standstill this afternoon," Malik said. "If an outage of this magnitude can strike Google, the company with a fearsome infrastructure, I wonder who - if any - can plan for the worst.

To be fair, with the exception of Twitter, outages are pretty rare. I've used Gmail for years now, and yesterday's disruption was the first time I've had to revert to my backup web-based email service, Yahoo Mail. (Memo to Jerry Yang: This is not a business strategy.) Today, some 20 million people trust Google to keep, protect, and make their emails available, which it has done largely without incident, until yesterday.

Like other cloud computing advocates, Google says it can manage, protect, and make available your data better than you can. Based on recent history, I'm not convinced.