Internet Detectives
From Interdex, the community-edited guide to the local internet.
The Internet Detectives are a loose coalition of local internet users who search the internet for information about stupid, disliked or mysterious people. The techniques of internet detectiving are not complex, and even amateurs have uncovered significant intel. While there is a website, most internet detectiving takes place on IRC in order to achieve more rapid collaboration. Notable accomplishments include the discovery of Muse's true identity, the revelation of BohemianSavant's obesity insanity, and researching ISPs and web proxies used by Booters and ZAF.
On the Something Awful Forums, "internet detective" usually refers to morally outraged people who attempt to dig up information on a poster for the purpose of inconveniencing them in real life.