No! They're relatively rare, under most circumstances. The spin has to be imparted in just the right plane, for a cube to stand on one corner and spin. As for "skill" I've never claimed any "skill" for throwing the dice. I just notice things that most people don't. In the early 80's, they changed the protocol for shuffling the cards in blackjack, and when they did, that game, was not as much fun to play anymore.