Many people tend to forget faces, events and more. In fact, we find ourselves confronted with a real limit of our brain, which only stores certain types of data, leaving the rest. In most cases we find ourselves confronted with friends, relatives and colleagues who do not digest this characteristic. 

If you forget something it means that you did not consider it important, here is the accusation that is generally addressed, but a study by the University of Toronto has carefully analysed this sort of mnemonic disorder.