As ShyTorque says, it is probably one of two things we, as helicopter pilots, would worry about failing the most, save for a rotor blade departing in flight. Ok so three. But a main gearbox failure (we don't carry a spare) or a tail rotor failure (for which we can only practice in the sim, and then its what the computer modellers/engineers and designers 'think' will actually happen).
My personal worry is a tail rotor failure, everything else we are pretty much well trained for, but in this day and age of modern technology, the 169 design does appear very simple. Too simple?