The owner/pilot had recently purchased the high performance, complex airplane, and he wanted to have another pilot accompany him while he familiarized himself with the airplane's flight and operational characteristics. He contacted a flight instructor, who was referred to him by another individual, to fulfill that role. Based on discussions with the owner, and the owner's significant number of flight hours, the instructor planned to perform in the role of safety pilot, as opposed to providing instruction. The airplane was parked in a row of aircraft that was separated from another row of aircraft by a strip of pavement about 60 feet wide. The airplane pitch and roll flight controls were of the "throwover" design, where there was only one yoke, which could be shifted to either the left or right cockpit position. The right cockpit position was not equipped with brake pedals. The owner took the left seat, while the safety pilot took the right seat. The owner's preflight and pre-start procedures all seemed normal and uneventful, and did not give the safety pilot any reason to more closely observe or doubt the owner's abilities. According to the safety pilot, the engine started "very aggressively," increased to a high rpm, and the airplane immediately began moving rapidly forward out of its parking spot. Once the safety pilot realized that the airplane was accelerating towards the row of airplanes on the other side of the pavement, he moved his left foot over and tried to apply the brakes, in part by stepping on the owner's right foot. After the airplane had traveled about "10 to 15 feet," the safety pilot also fully retarded the mixture control to cut the engine. The airplane continued across the ramp, and struck a parked, unoccupied airplane. The parked airplane received substantial damage to its fuselage and wing structure. The left wing of the accident airplane was substantially damaged. The safety pilot recalled that prior to and during the engine start, the throttle control appeared to be in a sufficiently retarded position for engine start, but the owner reported that he had positioned the throttle control inappropriately for engine start. Postaccident examination of the throttle control system did not reveal any mechanical anomalies that would have precluded normal operation.