Sadly, I'm going to agree with
@Chelsea FC here. Based only upon the match, it's in your best interest to tell multiple programs that you are their number 1. As mentioned above, some programs may ignore it and then no benefit. But if some increase your ranking based upon it (which they really shouldn't do -- their best ranking strategy is to rank applicants in the order they want, ignoring applicant preferences), perhaps because they want bragging rights of "I filled in my top X spots", you may benefit from telling multiple programs.
Can this hurt you? Probably not. PD's are not likely to compare notes. When you match somewhere and other programs are upset because you clearly lied, there isn't much they can do. But they could send copies of your #1 email (to them) to your new PD. GME is a small world, many PD's know each other. Your new PD might see this as unprofessional behavior. You won't lose your match over it -- but you will start with a big strike against you -- not a great way to start a new job, and you'll be in trouble if anything similar happens again.
It's also possible they could report this to your medical school. Would they consider it unprofessional enough to cause a problem? Probably not. But it could.
So the main point is this: If you send multiple #1 emails, you'll then start worrying after the match that this was going to come back to haunt you. You really don't want that. So send one, or none, and live with it. My 2 cents. That and a dollar will get you a cup of coffee.. Not at Starbucks, but somewhere. Not good coffee, but you can't have everything.