On August 28, 2004, about 0830 eastern daylight time, a Piper PA-30, N888LC, was substantially damaged during the takeoff roll at Cynthiana-Harrison County Airport (0I8), Cynthiana, Kentucky. The certificated private pilot was not injured. Day visual meteorological conditions prevailed for the personal flight, destined for Mount Sterling-Montgomery County Airport (IOB), Mount Sterling, Kentucky. No flight plan was filed, and the flight was conducted under 14 CFR Part 91. According to the pilot, an annual inspection of the airplane had just been completed, and the airplane had not yet been flown. The pilot completed a preflight inspection, noted no anomalies, and then boarded the airplane. He started the engines, taxied, and completed the run-up checks. The pilot did not identify any problems with the airplane during the taxi or run-up checks, so he taxied onto the runway, applied the brakes, and set takeoff power. He then released the brakes, and the airplane began to accelerate down runway 11. The takeoff roll progressed without incident until just prior to becoming airborne, at an airspeed of about 70 knots, the airplane yawed to the left. The pilot applied right rudder, but the airplane continued off the runway. He then closed the throttles and applied maximum braking. During the deceleration, the left wing contacted a windsock pole, and shortly afterwards, the airplane came to a stop. Following the accident, the airplane was taken to a repair facility at Highland County Airport (HIO), Hillsboro Ohio. There, a mechanic noted that the parking brake linkage on the left main landing gear was not connected properly. Also, the left main gear brake check valve was inoperative, which resulted in constant pressure being placed to the left brake calipers.