What about intentional over use of vibrato? I caught someone doing this at an open stage last Friday. He had excellent control over this aspect of his singing voice but used this ability to showcase his skill in every song he sang. So, instead of just singing his songs, they were merely used by him as springboards for his vocal calisthenics. While there's nothing inherently wrong with showing off your skills at an open stage, it was a little like hearing a guitar player use the same lick to display his skill in each of five consecutive songs. It's great the first time but loses something with over use and can become a genuine distraction. I found myself wishing he would throw aside his vocal skill and just sing.