I got a comment regarding my article Is Scientology A Cult?. The comment said a lot and you can read it here, but the main thing in it that I want to address is the author's depiction of "brainwashing". This term gets thrown around a great deal and it seems to have whatever definition the person using it wants it to have. Someone buys a used car that turns out to be a lemon and they accuse the salesman of "brainwashing" them. A family member joins a new religious movement and their relatives claim they have been "brainwashed". We see it used in movies and mentioned in books, so I thought this a good opportunity to address what it really is.
The term "brainwashing" (sometimes relabeled "mind control", "mental manipulation" or mental destabilization") is a term that is used by anti-religious extremists and self-appointed anti-religious experts as a tool of discrimination against new religious movements. The term was originally dreamed up by a CIA agent to describe the phenomenon of Americans in Korean POW camps making anti-American statements and in some cases even remaining in Korea after being released. The fact that only 21 out of 20,000 refused to return home was not given much publicity and the impression was created that "brainwashing" was an effective technique that threatened the very foundations of democracy. 
In the 1970's the "anti-cult movement" (ACM) hijacked the term and changed the definition so it included almost any human activity that involved changing somebody's mind. It could be applied to the entire spectrum from salesmen to torturers. It thus became a tool for the ACM in its quest to legitimize its activities and make money. 
The idea that the ACM created, was that people were forced into "cults" by the use of "brainwashing" and that once in they would robotically follow whatever orders the cult leader gave them and that they could never leave. Religious scholars who actually did research into the phenomenon of people joining new religious movements and then leaving them observed that the most controversial groups criticized as "cults" (including Scientology, the Hare Krishna Movement, and Reverend Moon's Unification Church) had a high turnover rate, a fact hardly compatible with their possession of "magical" techniques for keeping members within the fold. 
In the United States the theories the ACM had used to validate their abusive practices, such as kidnapping and coercion, suffered a death blow in 1987 when the report from the "APA Task Force on Deceptive and Indirect Techniques of Persuasion and Control" (DIMPAC) was rejected by the American Psychological Association. The report had been prepared by some of the leading lights in the ACM and it heavily promoted the "brainwashing" theories. The reviewers from the APA threw it out, stating, "it (the report) lacked scientific rigor and an evenhanded critical approach to carry the imprimatur of the APA".
In his comments on the report an external advisor to the APA, Benjamin Beit-Hallahmi of the University of Haifa, stated that "lacking psychological theory, the report resorts to sensationalism in the style of certain tabloids" and that "the term 'brainwashing' is not a recognized theoretical concept, and is just a sensationalist 'explanation' more suitable to 'cultists' and revival preachers. It should not be used by psychologists, since it does not explain anything". , 
One of the DIMPAC authors, Margaret Singer and an associate, sociologist Richard Ofshe, subsequently took the novel approach of suing the APA and the ASA (American Sociological Association) for having rejected their theories. The suit included respected scientists who had criticized the shoddy research methods of the two. Singer and Ofshe complained that the defendants had conspired to deny them employment as paid expert witnesses in the anti-religious community. The judge dismissed their complaint as "absurd".
And so the "brainwashing" theory died in the United States. In Europe however, which does not have a history of religious tolerance, the "brainwashing" theory is still bandied about by anti-religious groups, however, religious scholars do not support the theory. , 
So, according to experts, including the American Psychological Association and most religious scholars, "brainwashing" is a myth created to excuse attacks upon groups with different ideas to those of the attacker.
-  Brainwashing and the Cults: The Rise and Fall of a Theory
-  "Brainwashing": Career of a Myth in the United States and Europe
-  APA Memo of 1987 with Enclosures
-  Documents on Brainwashing Controversies and the APA