Start-ups and new Web 2.0-based service providers, such as San Francisco-based Cloudize Inc., are among the biggest users of cloud storage, at least for the time being. Cloudize bills itself as the first SaaS-based file collaboration tool focused on small to midsize enterprises. CEO Edwin Fu says the tool was designed to centralize all of a company's files in a cheap, scalable and collaborative way.

One of Cloudize's Web 2.0-based applications lets users of Salesforce.com -- the granddaddy of software as a service -- store and share data, such as big sales presentations and video, in the public cloud. San Diego-based Nirvanix provides the public storage cloud behind Cloudize.

Fu, a former Salesforce.com employee, describes that company's users as "low-hanging fruit" when it comes to signing up cloud storage customers. "We picked the Salesforce.com audience because they're comfortable with SaaS and SaaS-based storage," he says. "They already have their most sensitive contact data in the cloud. What we're doing is taking the next step."

On the larger enterprise side, cloud storage customers are fewer and farther between. "We are in the very early stages of adoption. Typically, when we're talking to customers, we're talking with classic early adopters," says Nirvanix's Ziernick.