As stated before there are alot of variables for things like this to happen. I saw a BJJ black belt get tapped by a purple belt and a blue belt one right after the other before. I know the BJJ black belt and he is very good. He is also a Judo BB so he is very good all around. However he had been coming off a back injury where he had surgery and this was the first time he had rolled in about a year and a half and 9 months after the surgery. Also he was giving up about 30 pounds to the other guys and definetly looked tired when rolling with them. So my point is yes although we think of black belts as this high level that only other black belts can touch we also have to consider other factors when something like this happens. Most of the time there is something going on there (injury, weight...ect) that has evened the playing field enough to allow the lower belt to win. I am a purple belt and have trained for over 5 years now. I have scored on my black belt instructor many times but never once tapped him out during a live roll.