In a way this is one of those "D'uh!" moments -- we've all seen (and most of us have made) honest errors and dumb mistakes. Laziness, foolishness, sloppiness, and most of the other foibles you care to name can cause users to open the wrong e-mail, enter information in the wrong place, do any number of things that expose themselves and their colleagues -- and your business -- to threats.
What makes the experts' insights of particular interest was the degree to which user distraction was also cited as a vulnerability.
We've all seen that, too -- trying to climb out from under a mountain of work, racing through e-mail, clicking-and-grabbing to make a deadline or hit a quota... whatever the reason, it's all to easy for even diligent employees to make a mistake and expose your business to unwanted intruders, whether it's a virus or a pair of prying eyes.
Might not be a bad idea to send out a heads-up e-mail reminding everyone to look and think before they click, and make sure they understand that this is an all-the-time rule, no matter how distracted, overworked, or deadline-harried they are.