What's most worrisome about the finding is the difficulty, past a certain point, in defending against accidental data loss.
Obviously, many of the same procedures, policies and practices that guard against data breaches can have an effect on reducing and perhaps even limiting the accidental dispersal of confidential information.
But the sheer spread of employee connectedness and access, and, in turn, employees' embrace of that connectedness makes it all too easy for accidents to, well, happen.
All the more reason to review and, I suspect, dramatically tighten your accesses. Most of your employees may not need access to most of your information -- and most of them most definitely don't need access to your most confidential or sensitive stuff.
At the same time, and for the same reasons, review and reinforce company information access policies -- and especially e-mail and other data-transmission/transport policies.
Not a bad idea, either, to review employees' computer skill levels (and habits) while you're at it. Knowing how much they know (or don't know) about how to use their equipment safely and securely could give you some insight into whether or not your otherwise dependable and trustworthy employees are (data) accidents waiting to happen.
The complete IDC/RSA Data Leak Report is here.