Okay.. I saw a guy with a 40% plane at the 2005 Cactus Classic IMAC contest. Apparently either the motor mount bolts or the firewall came loose. Both the choke linkage and the throttle linkage bound up in the full throttle position. You could hear the thrashing of the engine trying to come off the airframe. We all knew it was just a matter of time until something really bad happened. A couple of minutes went by while he was trying to keep some assimilance of control. I'm sure it seemed like hours to him. Eventually, a loud crack or pop sound was heard. The engine seperated from the airframe. Good thing it was out over the field. Needless to say, neither the plane or the engine made it out alive. Had he had a way to shut down the engine, he could have safely landed and made the necessary repairs for a couple of bucks.

You can say what you want about mechanical linkages, but the norm is, if it can happen, it will. For me, the extra $50 is worth every cent knowing I have a positive way of shutting down my engines.