Rule #1 of Snowboarding
Don't drop your board.
This is something I've always told people who are new to hiking and snowboarding. Most have heeded my warning and no further explanation was needed. A few have not. One was my little brother. While hiking up the Evergreen Ridge at Solitude, he bobbled his board and down it went. We later found it hidden in a tree well. Another incident involved a newbie loosing his board on the Highway to Heaven traverse. It didn't stop until it hit the lake.
This weekend was the third incident. Because we weren't hiking, just crusing groomers, I didn't feel it necessary to give the first rule yet. Little did I know. After a fall on a black diamond run, the victim (name is being withheld) had to walk to the top of a small hill that he was unable to make it over the top of after his wreck. Upon reaching the top of the hill the victim dropped his board on the snow which immediately started it's decent without him. On hearing my expletives the victim made a valiant attemp to recapture his board, but despite his diving to recover it the board slipped out of his grasp.
I was actually on a pair of skis yesterday and I pushed off after the board as fast as I could. I quickly got behind the board but was unable to get in front of it and I was skiing as fast as I could. (Also, I'm a snowboarder mostly and therefore not the world's greatest skier) I began yelling down the mountain at some skiers below us to get out of the way. My adrenaline was pumping as all I could envision was the board hitting a mogul and decapitating some innocent 5 year old. One of the skiers below me saw the board coming and valiantly put himself in front of the projectile. The board hit him in the ski boots and cleaned him right off of his skis only to continue it's decent.
At this point I was able to get in front of the board and was able to tackle it. The victim slid down the hill to where we were, a solid 500 vertical from where the missile was launched and I immediately informed the victim of Rule #1.