One relates to real clients in filmed or taped clinical interviews. There are benefits and drawbacks. The benefits are, of course, that a real client with real issues presented spontaneously provides a demonstration closer to reality than an actor can working from a script, as my early experience had, at least in that instance, demonstrated. Additionally, a therapist is not an actor and is not working from a script, only from his or her own theoretical position, practice and personality. Real people talking about their real issues are more interesting and provide some surprises that allow a therapist to be challenged.
Real clients talking about their personal concerns are useful for ongoing research, as well.
The language and the body language of the client and the therapist, and the spontaneity of the session, create a resource for research that a planned, scripted and acted film or tape maybe cannot. Like the poet Keats' Grecian Urn, a film may be a fixed thing, forever the same, but if it is a good film and if it is true, the viewer and the researcher will discover that with each viewing and examination, something new is discovered or some new meaning emerges to enlighten and instruct. The disadvantages of a real client are equally obvious, but very significant. If a client does not have sufficient ego strength, it could be a negative experience for him or her. It is important to use great care in selecting someone.