After all, data about money can't be more important than money itself and money safeguarding/management has already outsourced to banks since, when? always?
"Next time there's a server security breach, I'll call my accountants to come fix it right?"
How's this any different to a physical bank security breach (aka robbery)? Next time the bank your accountants work with is robbed will you call them to fix the mess too?
You should look into how much people trusted banks with their money before the advent of FDIC. People trust banks with their money because the government is insuring it against theft or loss. No such guarantee comes with Cloud storage.