The high-wing, tailwheel-equipped airplane had just been signed off on its most recent annual inspection, and the pilot/owner had also topped off the fuel tanks before he flew it about 10 miles to a friend's private grass/dirt airstrip. The pilot described it as a "one way" strip, explaining that the landing direction was "uphill" and the takeoff direction was "downhill." The pilot had operated into and out of the airstrip about 20 times previously. All those flights, as well as that day's inbound flight and landing, were uneventful. After boarding and start up, the pilot back-taxied to the top of the rise that constituted the beginning of the runway. That section of the runway was more steeply sloped (downhill) than the rest of the runway. As the pilot reached the beginning of the runway, he made a 180-degree left turn, and began the takeoff roll; he did not straighten the tailwheel prior to application of takeoff power. As soon as the pilot added takeoff power, the nose "went about 15 degrees left." The pilot continued the takeoff attempt, and tried to recover the desired ground track by application of full right rudder. The pilot saw that the airplane was headed for a golf cart, with a person seated in it, that was situated about 80 feet off the left side of the runway. The pilot opted to turn more sharply left in order to avoid the cart and person, and this action took the airplane on a track that was more divergent from the runway axis. The left main landing gear struck a hummock and fracture-separated from the airplane, which resulted in lower fuselage and left wing ground contact. The airplane slid to a stop, with substantial damage to the fuselage and left wing. The pilot stated that the wind was "way under" 10 mph, coming onto the right side of the airplane during the takeoff attempt. He reported that he did not abandon the takeoff attempt at the initial veer off, because he was concerned about the airplane nosing over onto its back during an attempt to stop. One passenger reported that the initial directional excursion was "almost immediately" about 45 degrees off the runway axis. Post-accident examination of the airplane did not reveal any pre-impact conditions which would have precluded normal operation. Review of weight and balance information indicated that the center of gravity was very slightly forward of the forward limit, and the airplane might have been very slightly above its maximum certificated takeoff weight. Neither condition would have contributed to the loss of directional control.