To say that Apple co-founder Steve Wozniak isn't a fan of cloud storage would be a considerable understatement. Following a showing of Mike Daisey's one-man monologue known as The Agony and Ecstasy of Steve Jobs last week, the Woz voiced his opinion with regards to storing personal data off-site and the trouble that lies ahead.
In short, Wozniak said he thinks the idea of everything going to the cloud is horrendous and there will be a lot of problems within the next five years. The problem, as he highlights, is that cloud users forfeit ownership of their data - it's signed away the moment you agree to an EULA. He wants to feel like he owns things and that people tend to believe that because they access stuff from their computer, it's still theirs.
Depending on whom you ask, cloud storage as a backup solution isn't a terrible idea so long as it isn't your only means of backup. An unfortunate but perfect example of this recently occurred as Wired writer Mat Honan's iCloud account was compromised by a hacker.
Within minutes, the hacker had locked him out of his account and remote wiped his iPhone, iPad and MacBook Air. Judging by his blog post, it sounds like he might not have had a recent backup of his data either. Furthermore, his Google and Twitter accounts were also compromised and since his phone is linked to his Google Voice account, that service was also interrupted.
The moral of the story is to back up your data often and in more than one location.