The recent flooding in Canmore, Calgary, Manhattan and disasters elsewhere only serve to underline the importance of backing up your important digital files, and then backing up those backups. Fires happen. Floods happen. Power surges happen. Thefts most definitely happen.
There are so many ways to back up your data these days, and each method has its own pluses and minuses. The best approach would be to pick more than one system so you meet these three criteria: 1) all data is backed up at least twice; 2) at least one backup has to be stored somewhere else (e.g. your home if you're backing up an office computer, or your office if you're backing up your home computer; and 3) your files are backed up in a logical way (with some encryption applied as a whole, or to sensitive files) and on a regular basis.
First of all, I always recommend an external hard drive — or better yet an external hard-drive hooked up to a Pogoplug (www.pogoplug.com) so you can access the data remotely or use it as a home server for multiple computers.
Storage is incredibly cheap these days, and you can pick up a two terabyte (TB) external drive for about $80. At those prices it also wouldn't hurt to have a second external hard drive to periodically back up your backup — and to leave that second drive somewhere secure that's away from your house or business. One backup would be used daily/weekly, while the second drive would be used once a month.
The cloud is also a useful way to store your data off site, but it has limitations and the costs can be high.
For example, you can get 2GB of cloud space at Dropbox for free — but that's going to fill up fast if you start using it to save photos and video. The Dropbox Pro plan is $10 a month, which is considerably more expensive than an external drive after only eight months.
If you assume your external drive is going to last five years at minimum (most will last a lot longer than that) then the cost of 2TB works out to around $14 per year. A cloud service for the same amount of time would be $600 for just 100GB of storage space.
Another limitation of the cloud is your own bandwidth ceiling. Most plans in Canada are capped at 150GB to 250GB a month, and a lot of that is already in use if you stream movies and music, Skype relatives, play video games online, spend a lot of time on the web, and so on. If you're coming close to your cap, repeatedly backing up large files to the cloud could put you over your limit.