Importance of Thank You Letters

How important are thank you letters when it comes to OMFS residency match. Can they influence the rank list? Obviously, I can't imagine they hurt you but can they help? Can it also hurt you if you decide not to send them? I was also told anecdotally not to send them by a couple colleagues this cycle. Let me know your guys thoughts.
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Tags: Dental Residents and Practicing Dentists Source Type: forums