A regrettably common practice in academic writing is to cite papers because someone else cites those papers, without having read them yourself. Justin warns about this in his book on writing for computer science, and I know he personally has a few good anecdotes. The practice is particularly amusing when the paper is incorrectly referenced or simply doesnt exist; the original citer has made a mistake, and this has been blindly carried forward by their imitators. Via Edel Garcia comes The Most Influential Paper Gerard Salton Never Wrote, an article by David Dubin tracing the history of the vector space model as applied to the field of information retrieval. In this article, Dubin points out that a highly cited paper, A Vector Space Model for Information Retrieval, published by Gerard Salton in 1975 in the Journal of the American Society for Information Science, does not in fact exist.
That is an extreme case, illustrating the deeper problem. Too often, people cite papers as sources for conclusions opposite to the ones made. Or cite a conclusion as support for their own arguments without any sign that the methods inside the paper may directly contradict those arguments. This, of course, is most notable when the methods are not presented in any detail, or are hidden in supplementary material, as routinely occurs in "top-tier" journals.
(via Michael Nielsen)