My ex (who I lived with for three years) used to do this. I would plug my earphones into the computer to watch a video, he would start chatting some s**t. God, that was annoying... -_-

Usually I will either take one earphone out, or just turn my iPod off, just to be polite. I will always at least take both earphones out when I get to the tills at Tesco. It's only manners.

What annoys me is people driving with earphones in. Don't you have enough to concentrate on without stuff blaring in your ear?