Well, file-syncing is very convenient, but it's not a backup.
Dropbox offers the same functionality of Google Drive and Microsoft OneDrive (was SkyDrive). Essentially they're each the same as the other.
A very effective backup option is an external hard drive (well...two. One on-site, the other at home. Swap out over the weekend.)
A TRUE backup plan involves the 3-2-1 plan:
-At least three copies,
-In two different formats,
-with one of those copies off-site.
http://blog.trendmicro.com/trendlabs-security-intelligence/world-backup-day-the-3-2-1-rule/
Sorry, I'm a bit of a backup fanatic :angel: (in-house server, NAS mirror, online backup, two-drive backup...one at home...one at work). That way I'm protected against data loss from fire/theft or natural disaster.