In reality, Dropbox, Skydrive, and other cloud services should be treated as a type of media, just like BD-ROMs, tape, SDD, HDD, and even hard copy.
The trick is to use different media to protect against different things. My Blu-Ray disks protect an archive against tampering or CryptoLocker (barring a hack that flashes the BD burner's ROM to allow the laser to overwrite written sectors.) However, they have to be maintained in a good environment with a good indexing system. My files stashed on Dropbox bring me accessibility virtually anywhere... but malware that erases files could wipe that volume out in no time.
Similar with external HDDs. Those are great for dealing with a complete bare metal restore, but provide little to no protection against malware. Tape, OTOH, is expensive for the drive and requires a fast computer, but once the read-only tab is flipped or the WORM session is closed, the data is there until the tape is physically destroyed.
Of course, there is not just media... there are backup programs. This is why I use the KISS principle when it comes to backups. I use an archiving utility to break up a large backup into segments (with recovery segments to allow the archive to be repaired should media go bad), then burn the segments onto optical media.
I've found that using a backup utility can work well... until one has to restore, the company is out of business, and one can't find the CD key or serial number so the software will install. One major program I used for years worked excellently... then just refused to support new optical drives (as in ignoring them completely.) So, unless I can find a DVD drive on its antiquated hardware list on eBay, all my backups are inaccessible. I was lucky enough to find that and copy the data to a HDD, but using the lowest common denominator is a good thing.
Backups are the often neglected underbelly of the IT world. While storage, security, availability and other technologies have advanced significantly, backups on the non-enterprise level are still languishing behind in almost every way possible. It was only a few years ago that encryption became standard with backup utilities .
: With encryption comes key management, and some backup programs make that easy, some make it incredibly hard.