History of spam

Most probably (as found in most of the sources), the term spam originated from Monty Python's sketch (you can watch it here). The spam mentioned there is a processed meat.
In the sketch, every dish in the menu of the restaurant would contain Spam (usually repeated multiple times). This is also main property of the Internet spam- it's very often repetitive, which eventually causes great annoyance.
The first e-mail spam was sent in 1978, by Gary Thuerk. Meant to be sent over ARPAnet to about 400 people, the maximum number of receivers was 320, causing the remaining addresses overflow to body of the e-mail. Because it was first message of this kind,(quite unsuccessful because of the e-mail address list overflow), there were many different reactions to this message- the one most unliekly to happen nowadays, people who didn't receive spam, actually felt excluded.
But the spam wasn't really a problem until 1990's. There were a couple of very popular spams, of which many users have been a victim, or have heard of- you can read about them here.
Today spam is an issue on a much greater scale. Spam statistics can be found on many sites, and analysing them in a long-term scale, all show that the amount of spam is rapidly increasing. Here is a graph showing amounts of spam received by single user with multiple e-mail accounts (more scientific analysis to come later).