A study conducted by Diemar Otte, Hannover Medical University, Dept. of Traffic Accident Research, Germany, examined the impacts on the riders¢ helmets after a collision. 
The study revealed that many impacts (34.6%) are applied at the right (19.4%) and left area (15.2%) of the chin.
Thus, a rider has to bear in mind that jet helmets are handy, they are not sufficient though.  

This rider walked home after the accident. 

Another crash helmet ad.