The big problem with the ear-muff defense is that ensures that you will continue to take punches. Think about it for a second: you put both hands up against your head and either put your weight on your front foot or lay on the ropes. Your opponent is now free to whale away with impunity because you cannot punch back from that position. When he finishes- gets tired of- punching he can step back, take a breath and start again. See the Calzaghe/Lacy fight.
While on the subject of defense, let me address my pet peeve of the moment. That would be the "high and tight" position of the left hand as a defense against the right hand. You cannot throw a jab from there, not a proper left jab. What you can do is 'drop' your jab (as opposed to properly throwing it from the shoulder), at which point you get hit with a right. Also, keeping your hand and arm in that position requires muscular tension- especially if you have some guy yelling to keep it up there "strong", to block a punch- and this in short order will cause you to tire, drop your hands and get hit with a right hand. Last, you then have your vision blocked by your own left glove so you can't see the right hand coming, and isn't the punch you don't see the one that KO's you?
These days, using the left shoulder to block the right hand is treated like some type of magical thing that only some special boxers can do, that you have to climb some mountain to learn. It used to be the very first thing you learned about avoiding the right hand. Back when universities had boxing teams many of them published instructional books and you can still find them, and see if I'm right about that. Watch old fights. Nobody walked around the ring with their hands over their eyes.