SEAT FAILURE - REAR ENDED BY HONDA ACCORD AT APPROX. 40 MPH WHILE STOPPED ON A 2-LANE STATE HIGHWAY TO TURN LEFT . FOOT OFF BRAKE. PROPELLED FORWARD ABOUT 3 CAR LENGTHS. MASSIVE FAILURE OF SECOND ROW SEAT BACKS. SECOND ROW SEAT BACKS BROKE AND RECLINED AGAINST 3RD ROW SEATS. HAD THERE BEEN PASSENGERS IN THE 3RD ROW, THEY WOULD LIKELY HAVE SUSTAINED SERIOUS INJURIES. FRONT PASSENGER SEAT TWISTED LEFT. OTHER VEHICLE (HONDA ACCORD) HAD FRONT DRIVER-SIDE AIRBAG DEPLOYED AND DRIVER-SIDE SIDE AIR CURTAINS DEPLOYED.