I’ve noticed a strange thing since using v. 2.71 In car models, for example, I use a lot of nuts and bolts. My wok flow is that I make masters of these objects then duplicate them as needed. The original normally has a material assigned to it and I want the original material to be used in the copies unless I specifically change it. The attached screen-shot shows what happens: each duplicate has the same material, but with a new name.
Is there a way to prevent this happening?