Well, there's nothing in my philosophy that predisposes me to so believe, but it is certainly a wonderful concept:
Native Americans believe that the night air is filled with dreams both good and bad. The dream catcher when hung over or near your bed swinging freely in the air, catches the dreams as they flow by. The good dreams know how to pass through the dream catcher, slipping through the outer holes and slide down the soft feathers so gently that many times the sleeper does not know that he/she is dreaming. The bad dreams not knowing the way get tangled in the dream catcher and perish with the first light of the new day.
http://www.dream-catchers.org/