[Added June 2001]
I am reading a book by Daniel L. Schacter on memory(Searching for Memory: The Brain, the Mind, and the Past) and by searching online
about his work I have discovered that his last book is about the
“Seven sins of memory”. By the way,the book I am reading is really a magnificent book written by a researcher in the field. So I am looking forward to read
this new book. From an online search the seven sins summarize the
failings of our memory:

We don’t remember something because

1. We have forgotten it over time.This is the natural process of forgetting,which
   is present also for well coded material.

2. We didn’t pay sufficient attention at the time of encoding:where are my glasses?
3. The material is temporarily inaccessible.This is a retrieval failure .
   This seems to be caused by retrieval of similar items that interfere with
   access to the material.This is the well known tip-of-tongue phenomenon.

We remember something inexistent or in a distorted way:

1. Attributing an item to an incorrect source.Recalling events that never happened(false memories).
2. The recall is distorted by information provided by others.
3. The recall is distorted by present knowledge

We have unwanted memories

1. Remembering a fact that one would prefer to forget:for example depressed people tend to remember negative events.A trauma produces some physiological changes in the brain that results in the persistence of the memories of the traumatic experience.