After receiving taxi instructions from ground control, the Cessna 172, operated by the student pilot, with a flight instructor began taxiing from the tiedown location for departure. About the same time, the pilot of a nearby Cessna 150, also with intention for flight, observed the Cessna 172 taxiing toward his position and, believing the airplane had slowed to allow him to enter the taxiway, pulled forward from his tiedown location. Both airplanes were operating within a non-movement area where air traffic control clearance was not required. The Cessna 150 pilot reported that after moving forward, he briefly glanced at his instruments, which momentarily diverted his attention. When he looked up, he observed the Cessna 172 continuing to taxi toward him and attempted evasive maneuvers, but was unable to avoid a collision. The flight instructor of the Cessna 172 reported that while taxiing, the Cessna 150 pulled out of its parking position unexpectedly and without warning, directly into their path. He applied the brakes; however, the propeller of the Cessna 150 contacted the right wing of the Cessna 172, which resulted in substantial damage to the wing spar. The Cessna 172 flight instructor and the Cessna 150 pilot reported that there were no preaccident mechanical malfunctions or failures with either airplane that would have precluded normal operation.