If you're looking for a secure way of storing your data offsite, cloud storage is your best bet. These services allow users to store massive amounts of data online, and easily access the data from anywhere. Some services are very easy to use, while others are less user-friendly. Here, we weigh the pros and cons of 5 different options.
1. Dropbox: Dropbox is by far the most well-known cloud storage option, and it's easy to add more free storage onto your account by recommending the service to friends.
PROS
-Easy to add storage to base amount by recommending to friends.
-Intuitive usage.
-Easy to sync.
CONS
-Yearly price for 100 GB is a bit high.
-Once you hit your limit, hard to not purchase a Pro plan.
2. Google Drive: It took a while for Google Drive to launch and when it finally did, most users were quite happy.
PROS
-Easy to use, but not as intuitive as Dropbox.
-Cheaper than Dropbox and links to all Google Accounts, like Google Docs & Picasa.
-Gmail storage upgrade to 25 GB when you get a 100 GB plan.
-Works for PCs, Macs, Android & iOS devices.
CONS
-Not as intuitive as Dropbox.
3. Microsoft SkyDrive: SkyDrive is probably the cloud service that's been most placed in popular media. I've seen it mentioned in more than a couple of TV shows.
PROS
-If you still use Hotmail/Outlook mail, then it's easy to use and setup.
-Base free plan has 7 GB of storage.
-Cheaper than Google Drive and Dropbox.
-iOS and Android app for your mobile devices.
-Least intrusive service, runs almost on demand or in the background.
CONS
-Hard to connect to other platforms like Google Docs.
4. Bitcasa: This service is totally free, and there's a lot to like about that. Whereas some of the other services charge up to $100 per year for 100 GB, which ends up not being that much if you archive your photos, Bitcasa won't charge you anything.
PROS
-Unlimited free storage.
-Never run out of storage.
CONS
-No mobile app, only PC, Mac, Linux & Chrome.
5. Amazon Cloud Drive: This service is also available for computers only, no mobile devices, but it's similarly priced to SkyDrive. It costs $50 per year for 100 GB.
PROS
-Base free plan has 5 GB of storage.
-Cheaper than Google Drive and Dropbox.
CONS
-PC and Mac app only, no mobile app.
(Images: 1. Flickr member ilamont licensed for use under Creative Commons, all others as linked above)
100 DIY Ideas for the 3-Day Weekend
Danielle's Charming, Classic Walk-Up
Good Food to Share 
The Big Book of Small, Cool Spaces 
Apartment Therapy Presents 
The Eight-Step Home Cure 
White Enamel Flatwa...
How To Cook Fluffy, Tasty Quinoa
Perfect Summer Cocktail Recipe: Honey Bourbon Lemonade
I've been very happy with Dropbox. I don't use it for backing up my computer; I use Time Machine and Backblaze (automatic online backup) for that. For me, cloud storage is more about files that I'll need somewhere else, or files I'm sharing with clients. It's easy, intuitive, and automatic. Paste a file into the Dropbox folder, and it uploads. Right-click and get a download link to send to someone.
I am curious about Bitcasa: it looks like it's $10/month (at the bottom of their homepage, quoting some reviews). But I didn't sign up, so I couldn't find out for sure.
Data security is always a concern; we've all heard stories of security breaches with various companies. I'm careful to not keep account numbers and SSN, etc. in electronic files anywhere, but I do wonder what the risks are, if someone hacked into my online backup somehow?
I don't see a mention of Box (formerly box.net). They are more tuned for business uses, but they're still pretty good. I signed up during the time they had the 50GB promotion, which obviously isn't running anymore. 5GB for free accounts, and 50GB for ~$20/mo. They're a bit more expensive than the others, but they have a whole bunch of apps and websites with which they integrate: e-signing documents, workflow management, paperless office stuff, etc.
The best for me has been Sugarsync. A big comparison chart is available here: http://assets.sbnation.com/assets/1080740/bigchart-7.jpeg
Unlike dropbox or google drive, you can sync any folder and backup any folder. you can upload by email too. Sugarsync allows you to sync multiple computers and can sync folders between multiple computers.
Sugarsync gives 5gb, extra 0.5gb for using the link below, 2gb for inviting 20 friends,625mb for completing some simple steps and additional 250mb if you download and complete simple tasks on your smartphone app.Then there is the option of500mb per successful referral, 10gb if they take up a paid account.
I got 8.375gb (5+0.5+2+0.625+0.250) within minutes. Get it by clicking this link: http://bit.ly/KbjOKH
I'm not a fan of Sugarsync, but that is a popular one. I used Dropbox when I had an Android phone, but with my Windows Phone, I use the heck out of Skydrive and I love it. I also use Box from time to time which I believe is owned by HP and that works REALLY well for businesses and enterprises. Box has certainly gotten better for personal use, too and I find myself using it more and more.