The issue of corporate secrets is a difficult one. I was shocked when a friend told me about catching competitor's employees in a dumpster behind his office.
What makes the issue even thornier is the increase in outsourcing, temp agency workers, and employee transience. These people may have access to secrets or processes but lack the loyalty that your “lifers” have.
I've heard several urban legends about the original Coke formula (for example, only two people know it and they can never fly on the same plane). True or not, it's a good example of how strict you want to be with your own secrets. Although booking seats on two planes might be a little much, why not start with a good shredder and some employee follow-up?
At the same time, you can use these secrets to your advantage. Consider how companies — particularly tech companies — release secrets ahead of schedule to create a little buzz.