Have you ever rejected a manuscript, then changed your mind about the project and wanted it back? I've had this happen to me, where an editor will say a year or two later, "Hey, you still have that wacky manuscript available?"
Sure. It's a subjective business and we're subjective people. The thing that seems like a bad idea for today's market and today's frame of mind may strike an editor as just right in the market and frame of mind of two years from now.
Which is why you keep submitting. You should be giving a publisher the space of years before re-submitting, of course. This allows for (a) attitudes changing (b) staff changing and (c) your writing getting better.
The dark side of this healthy persistence, of course, is spamming publishers. Email spam is very obvious because many of your missives will immediately be forwarded to the department assistant. She, realizing it is spam, will delete it without reading it and possibly without replying. But the other kinds of spam are noticed and disliked as well, because, again, most of the mail is being opened by the same person.
You, Darth Manuscript. When you send in multiple copies addressed to various editors in the hope of reaching the right editor, we make sure your manuscript is not seen by any editor. I've been the editorial assistant and have trained later editorial assistants, and the force is with them. (And so is the paper shredder.)