DEAR HARRY: Since last spring, two of my friends' identities were almost stolen. Fortunately, both were able to stop it from happening, and neither was hurt. However, they have been urging me to be more cautious. As a result, I went out and bought a shredder. The directions in the manufacturer's literature would have me shred everything short of our paper napkins. I figure that they exaggerate in order to get me and others to overuse the shredders. What's the real deal here, Harry?