Puzzled by description of AoA malfunction theory on recent Lion Air accident
The Operations Manual Bulletin put out by Boeing suggests that this is a trim runaway event.  Airspeed and altitude measurements are affected by the angle of attack of the airplane.  The indicated airspeed will be lower in a high angle of attack situation.  The accident airplane was reading a higher angle of attack than reality due to a malfunction of some kind.  The new avionics in the Boeing 737-MAX correct the airspeed measurement for angle of attack so airspeed was reading higher than what it should have been.  As a result the automatic trim, which is set to keep a constant airspeed, kept trying to lower the nose since the reported airspeed was too high.  

The 737-MAX Operations Manual Bulletin included procedures to disable the automatic trim.  This runaway trim event occurred during the 3 flights before the accident flight but maintenance was unable to fix the problem.  

More information on the accident can be found at the Aviation Herald.