Anonymity on the Internet is obviously of great interest to would be whistleblowers, and those interested in their revelations:- dissidents. As of 2019, it is increasingly under threat by measures both legal and technical.
From 1993 to 1996, privacy advocate Johan Helsingius ran a widely used internet remailer, anon.penet.fi, which received emails and forwarded them, allowing people to comment anonymously on Usenet. After leaks by use "-AB-" about the Church of Scientology, in 1995, Interpol contact the Finnish Police, which demanded Helsingius turn over his data, which would have revealed over 300,000 identities. He reached a compromise with them, and turned over only the identity of "-AB-", Tom Rummelhart, a Scientologist and computer operator responsible for some of the maintenance of the Church of Scientology's INCOMM computer system. Helsingius shut down anon.penet.fi after further pressure from the Church of Scientology.
In recent years, large technology companies are using a range of measures to encourage users to login and provide identifying data.