Chain letter
Email instructing recipient to 'send to all your friends'
A chain letter is a letter distributed across the internet, carrying as part of its message a call to forward the message on to more people. Subjects of the letters are diverse, ranging from amusing jokes to political tirades to tragic stories or promises of free money. The linking theme is the need to forward the message.
Famous chain letters have included fake messages from major corporations such as Microsoft, promising large amounts of money to those who forward the message to enough people, as well as virus hoaxes. Chain letters use up large amounts of bandwidth and also risk exposing email addresses to spammers - the common practice of using cc rather than bcc, and including full histories in the mails, means that some chain letters can contain thousands of email addresses.