Short answers, pulled from the story.
The first recorded instance of fandom occurred in 1893 when thousands of people gathered in London to mourn the death of Sherlock Holmes in The Final Problem. This event marked one of the earliest recorded instances of a subculture forming around a shared obsession with a media property and predates the term fandom by decades.
The first World Science Fiction Convention took place in 1939 and created the first formal structures for fan interaction. These gatherings established clubs and conventions that became the blueprint for all future subcultures and evolved into massive events drawing tens of thousands of attendees.
Fans of the Grateful Dead began trading concert recordings and discussing the Wall of Sound on ARPANET in the late 1960s to the early 1970s. The Internet Archive began to add Grateful Dead shows in 1995 and online tape trading communities such as etree evolved into P2P networks trading shows through torrents.
The brony fandom emerged in late 2010 and early 2011 on the imageboard 4chan and adopted the name brony as a portmanteau of bro and pony. They developed their own distinctive vernacular and create personalized pony characters representing themselves called ponysonas.
Fans of Star Trek organized to save the show from cancellation in 1968 and similar efforts were made for Cagney & Lacey in 1983, Xena: Warrior Princess in 1995, and Roswell in 2000 and 2001. The Firefly fandom generated enough corporate interest to create a movie after the series was canceled and fans of the show Chuck launched a campaign to save the show from being canceled using a Twitter hashtag.
The book Fifty Shades of Grey by E.L. James was published by Random House in 2012 and was originally a fan fiction of the Twilight series published on FanFiction.Net. James rewrote the story to take out any references to Twilight and self-published on The Writer's Coffee Shop in May 2011 before selling over 100 million copies.