Basically, a human flesh search engine is a group of people who, through social networks, blogs, forums etc. find the identity of a specific person.
Excerpt from English-language wiki:
Human Flesh Search is a phenomenon of massive researching using Internet media such as blogs and forums. It is based on massive human collaboration. The name refers both to the use of knowledge contributed by human beings through social networking, as well as the fact that the searches are usually dedicated to finding the identity of a human being who has committed some sort of offense or social breach online. People conducting such research are commonly referred to collectively as "Human Flesh Search Engines".
