Answer: Chain Letters

The very first formal netiquette proposal RFC 1855, a memo released by the Internet Engineering Task Force in 1995, offers a variety of guidelines for proper conduct on local networks and the Internet. Among the many proposed rules of conduct, the following violation was considered grave enough to merit revoking a user’s network privileges:

Never send chain letters via electronic mail. Chain letters are forbidden on the Internet. Your network privileges will be revoked. Notify your local system administrator if your ever receive one.

We can only imagine what a wonderful place the Internet would be if such a stern stance on chain letters had been strictly enforced.