When virtual clouds first rolled in, there appeared to be little indication that a downpour of privacy concerns would follow.

Web surfers tossed photos into online albums, logged errands on digital calendars and sent work files to personal email accounts. To this day, we continue to fling tidbits of information across the web and into invisible storage lockers.

All this online data hoarding is known as "cloud computing," the process of using the Internet to ship files over to a remote server instead of just saving to a local piece of physical media, such as a hard drive.

Buoyed by early successes, tech companies have whipped up all-purpose cloud storage vaults where users can save an assortment of files to be accessed virtually anywhere with an Internet connection. Whether you're using a desktop, laptop or smartphone, the files are at your fingertips.

"If a bulldozer happens to run over my laptop, all the data on my hard drive is gone. But with cloud storage, all that data out there can be downloaded and I just pick up where I left off," explained Carmi Levy, an independent technology analyst.

The winds of competition have recently picked up among Google, Microsoft and Apple, which are all pushing their own respective storage systems. Other services such as Dropbox, iDrive Sync and SugarSync boast no-nonsense interfaces and devotion to a single task: backing up your stuff.

It's no longer necessary to carry around a pricey external hard drive, email spreadsheets and PowerPoint presentations to yourself for posterity, or fumble under a desk while trying to wedge a USB key into a computer tower.

Convenience aside, the mounting popularity of cloud storage systems has been accompanied by a chorus of privacy concerns. Most of the distress revolves around the idea of stockpiling personal information on servers hosted by third parties.

"As soon as you put files on a device that you do not directly own or a control -- which is basically what the web is -- it enters this amorphous state where you don't really know where it is, you don't know who has access to it," Levy said in a phone interview.

A torrent of criticism followed the release of Google's Drive system last week, as users dissected a confusing legal clause in its terms of service. The passage suggested files uploaded to the online service could become Google's property.

"So you save your amazing invention to Google Drive and they can claim that they invented it, right?" one Twitter user wondered after the service's launch.

Not quite, Google said in a prepared statement responding to the confusion.

"Our terms of service enable us to give you the services you want -- so if you decide to share a document with someone, or open it on a different device, you can," it read.

Levy noted that while Google's terms of use appear invasive, it's farfetched to think the search giant wants to make off with a person's PowerPoint presentation or vacation photos. Google is likely more interested in mining data to customize the advertisements that accompany its services, he said.

"The takeaway here is that when you sign up for any service, any third party or web-based service, it's your responsibility to read the terms of use," added Levy.

That said, there are dozens of other cloud-based storage systems available for web surfers who want a virtual filing cabinet accessible from anywhere with a web connection. Pricing depends on storage space, calculated in gigabytes, though most services offer a certain amount of space for free.

Here are how a few commonly used clouds stack up:

Google Drive

  • Available on: PCs, Macs, Android devices. Plans for Apple iOS devices in the works.
  • Space: Store up to 5 GB for free. Monthly rates range from $2.49 for 25 GB to $49.99 for one terabyte, not including any taxes or fees.
  • Pro: Designed to complement other services in the Google suite
  • Con: Many users might find the terms of use unnerving.

Microsoft SkyDrive

  • Available on: PCs, Macs, Android, Apple iOS devices.
  • Space: Up to 7 GB of free space. Pricing starts at $10 for up to 20 GB per year.
  • Pro: A generous amount of free space, designed to complement other Microsoft Office and Live services.
  • Con: SkyDrive used to offer a generous 25 GB of free storage, but users new to the service will have missed out.

Apple iCloud

  • Available on: Macs, iPhone, iPad, iPod touch and even PCs
  • Space: Users get up to 5 GB free. Paid storage ranges from $20 per year for 10 GB and $100 per year for 50 GB.
  • Pro: Appealing to those with other Apple products. All updates to your iPhone, iPad or iPod touch will sync up with the cloud, keeping files current.
  • Con: Maximum file size for free users is only 25 MB.


  • Available on: PCs, Macs, Android devices, iPad, BlackBerry, Apple iOS devices.
  • Space: Free accounts start at 2 GB, but users can earn more with referrals. Individual plans start at $99 per year for 50 GB to $199 for 100 GB.
  • Pro: This service is straightforward and easy to use, making it a good choice for those who don't consider themselves to be tech-savvy.
  • Con: Pricing plan can get costly, others offer more for less.