I asked him recently about the cloud. His description of the cloud (which he does not use for any of his own documents, photos, records, anything) is that it's like the Wild West in terms of security and privacy. It's incredibly easy to hack into and steal stuff off of, according to him, and he feels we've barely seen the tip of the iceberg of massive security breaches and identity theft.
He told me that the cloud is a great idea operationally, but its security is next to nill at this point.
Anyone who lulls themselves into believing they have security in today's world is in for a rude awakening. As to the cloud, I would never maintain anything there for which security was important. Things like music or books are fine.
As to other things, when credit card processors and major retailers can't maintain security, you're subject to their shortcomings but also to issues on any computer hooked to the internet at any point. Windows is subject to problems, Android is, and Apple/ipads and iphones are. The more popular they get, the greater the number of hackers going after them.
I personally do not use my smartphone to do banking transactions and seldom use my tablets. Plus I don't maintain that information in them. I treat it as if I'm using someone else's computer. But the thing I'd most advise is have a plan in place for when everything you have gets compromised. That means a list of cards and accounts and phone numbers or a service so you can notify everyone quickly. Also bank alerts are very useful.
As to the bolded comment above, I agree 100%. So does my IT officer. So do nearly all experts. It will happen to you so just be prepared to survive and recover. The banks are doing an incredible job to try to control and limit it. In the last five years, I haven't had it happen to me but I've had at least 6 times the banks cancelled a card and gave me a new one due to risk.