"After you initially install it, you don't have to do anything with it. You select which files you want backed up and how often you want them backed up, and it just happens," Roberson says.

Like most others, Mozy's service offers data encryption, but Mozy goes a step further by offering either a public or a private encryption key created by the user. The private key is stored on the user's computer, so if Mozy's data centers were hacked, there would be no key with which the thieves could unencrypt customer data. However, if consumers lose their keys, they also lose their data.

What some may see as a drawback to services like Mozy is that they require software to be downloaded onto a customer's computer. That software can have some complex settings and limit the number of file versions.

For four years or so, David Albrecht, a computer engineer from Illinois who is working on a master's degree, has used MozyHome to back up about 50GB of data on his MacBook Air laptop, and Amazon's S3 cloud storage service to back up a Linux home server.

"I think of Amazon's S3 as more of a pure cloud offering. I use it for Linux because it's easier to script and I don't think there's a Mozy-like tool available on Linux," he says. "S3 is a high-availability Web service, and Mozy is made for personal backup."