Where's your stuff?
"Be aware of the location of the file. When you put stuff into DropBox, it's no longer on your computer; it's been uploaded," she said. "Many people are unaware of that. Once they realize...it's no longer on their computer, but in a third-party data center, some people don't necessarily like that."
Conner was referring to the act of dragging a file into the Dropbox desktop application, which migrates it from the original machine to Dropbox's cloud. That file will no longer be stored on the original machine. However, if a file is uploaded from a user's computer to Dropbox via the web client or it is copied and pasted from the user's computer into the Dropbox desktop application, the document is still available on the original machine
Conner also advises users to find out how a cloud storage provider might use their data. "I don't want someone data mining by information for purposes I didn't intend it to be used for," she said.
You may want to know whether the cloud storage service runs its own infrastructure, or if it uses another cloud storage provider's data center? Do you care?
DropBox is thought to be on Amazon Web Services and SugarSync is rumored to run its own infrastructure, Gillett said. "Do you feel better that they're using an established third party that a lot in the industry have vetted...or would you rather not see them on Amazon?," he said.
If you're outside of the U.S. and want to make sure your data is not subject to the U.S.A. Patriot Act, you may want to make sure your files are not within the country's borders.
Many devices, one service?
Today, many consumers have more than one device running on different OSes, such as a Windows laptops, an Apple iOS device or maybe an Android phone. Make sure the vendor supports the devices you currently have -- or may want in the future.
"My whole house Mac, so the Apple iCloud makes more sense for us," Conner said. "If your house is more of a mix, Android and iPhones, maybe a more OS-agnostic service would be better suited to your needs."
Leading cloud storage providers such as DropBox, Box, SugarSync and YouSendIt, support multiple OSes, both mobile and desktop.
It's also good to find out who the service is targeting. While Box still offers consumer-class services, it has gone after corporate users with features an IT administrator would want, such as the ability to remote wipe documents from mobile devices and manage access to corporate servers.
File synchronization service SugarSync recently rolled out an iPad application for iOS users, allowing customers to synchronize data across Apple devices. It also supports Android, BlackBerry, Symbian and Windows Mobile applications.
There are a growing number of cloud providers now and more are joining the herd every day. For example, traditional backup providers such as Mozy, as well as anti-virus vendors like Trend Micro, are adding cloud storage and synchronization services to their product portfolio. If you're already using a backup service, check to see whether the company's offering -- or plans to offer -- file synchronization.
For example, Mozy's Stash provides users with unified access to files. TrendMicro turned its 2010 acquisition of U.K.-based Humyo into SafeSync. Citrix bought ShareFile, adding a business-class file storage and synchronization service.
While all the services offer encryption, if security's important you'll want to ask: Does the company encrypt the file before it's sent over the Internet?