For those who don't know, the phenomena of "spam" (useless/scam posts) first occured on Usenet. That's why the current absence of spam on Usenet is so remarkable.

Ironically, spam didn't kill Usenet. Rather, it was the fact that Usenet was so confining. All you could do with it was post what amounted to blog posts and files. In 1989, the first web browser was invented. After that, Usenet quickly declined as people learned that a web browser is 10k more useful than access to Usenet.