Here is what the NRMP has to say about this issue:
"It is a material breach of this Agreement for a participant in the Matching Program to make any verbal or written contract for appointment to a concurrent year residency position prior to the Matching Program. In addition, although applicants or programs may volunteer how they plan to rank each other, it is a material breach of this Agreement to request such information."
From:
http://www.nrmp.org/res_match/policies/map_main.html#restrictions
I think this wording is confusing. What is clear is that neither programs nor applicants may request of the other how they will be ranked.
By voluntarily telling a program that you will rank them #1, it is technically not a "verbal" contract since a successful match depends on them ranking you in the top (however many spots are available), though it implies to the program that if they do rank you in the top (however many spots they have), you will be matching with them. If programs rank you in their top slots, and you end up matching elsewhere because you didn't end up ranking them #1, have you now violated a verbal contract?
Also unclear is the opposite: if a program tells you that you are in their top (however many spots are available), this sounds like a verbal contract, right? If you rank them #1 and you don't match there, haven't they violated a verbal contract?
This is confusing to me because I have heard that it is OK to tell programs you will rank them #1, but in doing so, is this not a verbal contract, which is a rule violation?