I think I've mentioned this before, but it continues to happen more and more often: people keep sending us stories that we've already rejected, usually a year or two ago. In some cases, the author never received the rejection note, so assumed that the story was lost; I can more or less understand that, though the right thing to do in such circumstances is to query rather than resubmit. In some cases, the author has revised the story since we last saw it; I can understand that too, but the right thing to do in that circumstance is to provide a cover letter saying "I've revised this story extensively since you rejected it, and I think it's better suited to your needs now." Just resubmitting a story, with no comment indicating that it's a resubmission, especially if the beginning and ending haven't changed, causes me to assume that the author doesn't keep very good records. It also tends to annoy me, more than is really reasonable.
So don't do it, 'kay? I know, I know, you authors who read this journal know better than to do this kind of thing (except in the sort of rare accident that can happen to anyone). Preaching to the choir, Jed.