My wife used to wear one while driving. And she left it in the car. Didn't use it anywhere else. I think that's a good use. Now you can hook your phone up to the car and have phone conversations over the sound system built in. That's even better...unless you've got a car load of people and you're getting a call back from the doctor reporting that the STD test came back positive.
It is irritating to be on the wrong side of a one way conversation when people are talking on them things. I was in a hotel lobby waiting on the elevator. Guy walks up and asks a question. Out of the blue. Kinda of a loud and brusque, obnoxious type. I didn't have a clue what he was talking about. I ignored him. He asked again. I said "excuse me? Are you talking to me?" Dude got all upset that I was bothering him. "No! I'm on the phone!" like I was interfering in a private conversation. The ear piece was on the other side and I didn't see it. I couldn't help myself... "My mistake. I thought you were just a dumbass talking to himself. But I see you're just a dumbass talking to a gadget in his ear. Carry on."