People masquerade as Dr's when checking in the hope of an up-grade. Once heard about a guy who said he was a Dr and when his services were needed, transpired he was a Dr of philosophy!
Sure a Phd friend of mine is often asked on flights if she is a medic and they always accept her explanation. She says that, on occasions, she thinks it has contributed to her recieving an upgrade but that was ten years ago - it does not happen now.