I would like to share my latest AppleCare-Mac Genius encounter. After finding that people could see me but not hear me on FaceTime I contacted AppleCare yesterday. After some tests and elevating the call I was advised that it was a hardware problem. They scheduled an appointment at the local Apple Store to have my MBA 13 replaced. I visited the store today and the Genius quickly determined that the Bodyguardz strip on the left side was covering the mike and disabling it. I wasted a few hours on this problem and can hopefully spare someone else the hassle. I have also notified Bodyguardz.