Pseudonyms (i.e. "pen names") are widely used on the Internet, especially in some of the commercial online services. It is also possible to send messages anonymously, by sending them to an "anonymous remailer" which strips the message of all identifying information.
Pseudonymity and anonymity can be abused. For example, an anonymous defamatory message was sent to the Prodigy bulletin board in 1994, accusing Stratton Oakmont Inc., a securities investment banking firm, of "major criminal fraud" (Rosenoer 1997). Other immoral and illegal activities, such as sexual harrassment, personal threats, and money laundering, could be carried out by means of anonymous or pseudonymous messages.
However, it is important to realize that both anonymity and pseudonymity can provide considerable social benefits. Several famous authors are best known to us by their pseudonyms: Mark Twain, O. Henry, Voltaire, and George Eliot. Benjamin Franklin and Charles Dickens also wrote under pseudonyms. Anonymous political writing has also been important---for example, the Federalist Papers. People may choose to write anonymously, or using a pseudonym, for quite legitimate reasons, one of which is to preserve their privacy even as they express their views in public. The right to speak anonymously is part of the right to speak freely, which is protected by the First Amendment. Of course, this does not apply to non-protected forms of speech, such as libel, slander, and fraud. (Rosenoer 1997)