Exposing the dark side of cloud computing, Salesforce.com suffered an outage that locked more than 900,000 subscribers out of crucial applications and data needed to transact business with customers.

Salesforce, the 800-pound gorilla in the software-as-a-service jungle, was unreachable for the better part of an hour, beginning around noon California time. Customers who tried to access their accounts alternately were unable to reach the site at all or received an error message when trying to log in.

Even the company's highly touted public health dashboard was also out of commission. That prompted a flurry of tweets on Twitter from customers wondering if they were the only ones unable to reach the site.

Salesforce has long vaunted the speed and availability of its service as reasons businesses should dump their in-house customer relationship management applications and instead rely on its online infrastructure. Indeed, for those selling shoes or coffee, it can make a lot of sense to turn to someone else for IT support so you can focus on your core strengths.

But the outage, which Salesforce has yet to explain, also shows what can happen when close to a million subscribers depend on a single entity to handle some of the most important data in their company. Sure, plenty of organizations suffer hour-long outages, but they're generally spread out. Not so in this case, when a single disruption suddenly paralyzes a small fraction of the world's economy. Can anyone say putting all our eggs in one basket?

Real world sales forces are generally useless without real-time access to CRM apps. If cloud computing catches on the way Salesforce, Amazon, and the other cheerleaders say it will, this dark side is only likely to get worse. ®