Green Card spam
The ad two lawyers posted to thousands of newsgroups in 1994, turning commercial spam into a business model.
On 12 April 1994 Laurence Canter and Martha Siegel, a married pair of immigration lawyers in Phoenix, had a script post "Green Card Lottery – Final One?" as a separate article to roughly 6,000 Usenet groups. They offered paid help with the US diversity visa lottery, which anyone could enter for free. Mass postings had happened before, but this was the first done openly, for profit, and with no apology whatsoever.
The backlash was enormous: their provider was buried in faxes and mail until its servers fell over and it pulled the account, and Norwegian programmer Arnt Gulbrandsen wrote a cancelbot that deleted the posts. The couple responded with a book, How to Make a Fortune on the Information Superhighway. Canter was disbarred in 1997, partly over the affair. The technique outlived his career by a comfortable margin.