Personally I think it's a faux pas even if you have no intentions of ranking them. It's always good to show your appreciation towards your department, especially if a faculty wrote you a recommendation letter, or if they sponsored one of your interest groups, or if you rotated with their residents or faculty. Probably the only person to noticed if you stiffed them would be the program coordinator, but still... Just be generous and be appreciative, I think it goes a long way. And once you graduate, keep in touch the home school. Because bottom line, you never know where life will take you and when you will cross paths with these people again -- They may end up with an opening for a Faculty or fellowship position that fits 100% what you want.