From I, Cringely
Apple co-founder Steve Wozniak this week warned of the perils of depending too much on cloud storage and the general press reacted like this was: A) news, and; B) evidence of some inherent failure in cloud architecture. In fact it is not news (Woz never claimed it was) and mainly represents something we used to call “common sense.”
However secure you think your cloud storage is, why solely rely on it when keeping an extra backup can cost from very little to nothing at all?
No matter whose cloud you are depending on it will be subject to attack. Bigger targets get more attacks and something as big as DropBox, say, is a mighty big target, while that spare hard drive attached to a PC at your house (or my preference — the house of a friend) is generally a target too small to even be noticed.