Laud Humphreys, a sociology graduate student at Washington University in St. Louis, published "Tearoom Trade", a study of homosexual encounters in men's rooms (called "tearooms") at public parks. To gather data for his doctoral dissertation on restroom sex. 

 Humphreys pretended to be gay, and assumed the role of  lookout for the police. He also surreptitiously wrote down the license-plate numbers of participants in order to obtain their names and addresses. Then he waited a year, disguised his appearance, and interviewed about fifty of the tearoom regulars at their homes (sometimes in the presence of their wives and children), on the pretext of administering a social health survey. 

His descriptions of this second encounter made it possible for many of the men and their families to recognize themselves once the dissertation was published as a book. The subjects were never informed that they were subjects of research and private information was collected from them under false pretenses.  

The current human subjects regulations that protect people from civil or criminal liability, adverse effects on employability and embarrassment were written in response to this type of research.