The new version of the Diagnostic and Statistical Manual (DSM-V) includes a very useful description of Dissociative Identity Disorder, (also known as Multiple Personality Disorder) which is especially important for people who have suffered extreme childhood abuse - the commonest cause of DID - since they are often invalidated or misdiagnosed with schizophrenia or other psychosis.
The False Memory Syndrome people are petitioning the APA, who compile the DSM, to remove the diagnosis completely, and if that happened, it would serve to
1] further invalidate, isolate and marginalise survivors of extreme childhood abuse
2] further protect and validate the perpetrators of that abuse.
DID is a rare condition and there have been cases of misdiagnosis, but there is sound clinical evidence of its existence and to remove it would set the mental health care field back many years.