http://www.nytimes.com/2009/12/01/health/01dutch.html?_r=1&pagewanted=all
I'm sure you familiarized with the technique of mystery shopping. it's world wide used, specially in services like banking, insurance, etc. The idea is that someone impersonates a regular customer, go to the bank and report their experience.
Malingering one’s way into a psychiatric ward to report on conditions within was first tried in 1887, when Nellie Bly, a journalist got herself admitted to the insane asylum on Roosevelt Island in New York City.
It was tried several other times. The article is about a recent experience in Amsterdam. Many questions are raised here, namely the secrecy and implicit trust between patients and carers.