DrugMonkey has a fascinating post on citation practices. It's fascinating because all of the comments have come up in some research article or other that I've read, but many of the commenters don't believe the other commenters and many readers may be shocked/surprised at the whole thing.
You see, we talk a good game about the Mertonian norms, but what we might do in practice is sometimes quite different. Anyway, the thread is worth a look. Here are some links to things I've written on citing practices in science: