Great question Orthorover. Like you, I can't, in good conscience, accept two interviews for the same date knowing that doing so might deny fellow applicants a chance to interview. Personally, that seems unethical given how competitive this whole process is. However, I'm not naive enough to think that everyone share's this perspective. The swaps I posted would help me deconflict travel plans. Last minute cancellations are not viewed favorably by programs (ortho is a small community) and make it very difficult for others to scramble to fill that slot. All we can do is hope that our future colleagues will do the right thing and help each other out.