Then again, adcoms may prefer to send out an offer to someone they know will accept. This increases their offer to acceptance ratio, which I understand matters a bit.
That said, I think it is a bit over the top to notorize it. The letter itself is binding enough. I don't think they'll sue you saying "but...it was NOTORIZED!" Make sure you want to go there no matter what, because if you get accepted somewhere else you'd rather go, and then turn the letter of intent school down, you may get into trouble later on down the line, like residencies or whatnot. I think the medical community is smaller than you might think, and you don't want to make a bad name for yourself.