4) March 30 ARMM Massacre
Richard E. Depew is according to Wired's article, regarded as Usenet's major bincanceler (for removing binary files from nonbinary newsgroups) was connected with 1993 ARMM spam. He advanced the idea of semi-moderating the USENET groups, cancelling some posts that weren't written according to the rules. He developed a software, which main purpose was to help him do the moderation. Then something went wrong - his ARMM tool had a bug, so when he started it it sent couple hundreds of messages to the "appropriate" news.admin.policy news group. As Brad Templeton noted - "The very day ARMM was run, Joel Furr, as far as I can tell, was the first to call a spam a spam".
This was a trip to the memory lane for someone, and just a bunch of boring or interesting facts for others. Brad Templeton did a great research on Spam Etymology, and his study is the main reference for the mentioned moments in spam history. Keith Lynch runs a great spam related timeline, and the whole list can be found in the References section. You can learn lot of interesting information from the timeline:
June 1995 - Two coined words appeared - spamvertise (to advertise via spam) and spamware (spamming software)
August 1995 - List of 2 million email addresses is offered for sale
October 1995 - Mailboxes for abuse related contacts are opening (abuse@provider)
June 1997 - FTC spam hearing (more information)
July 1997 - news.admin.net-abuse.email starts with its work
October 1997 - RBL (Realtime Blackhole List) of spam sites appears. It is run by Paul Vixie.
December 1997 - List of 80 million email addresses offered for sale
May 1998 - UUNET (large Internet Service Provider) becomes a major spam source
July 1998 - List of 91 million email addresses offered for sale
Novemeber 1998 - Dotless numeric web sites (e.g. http://3448157907/xx12) are being used to make tracing harder.
June 2000 - Argentina (its TLD .ar) becomes a major spam source
November 2000 - Taiwan (.tw) becomes the spam capital of the world
May 2001 - UUNET finally ceases being a major spam source