Follow Friday started like other Twitter staples--with the users, by the users. According to Twitter lore, it was this tweet that began in back in 2009 by Micah Baldwin (@micah), founder of another tech / digital content start-up called Graphicly:
I am starting Follow Fridays. Every Friday, suggest a person to follow, and everyone follow him / her. Today it's @fancyjeffrey and @wiredone.
The hashtag was soon added and the whole abbreviated to save character count. #FF is a way to share your favorite accounts with your followers. It's also used as a way get noticed. Say you like somebody with a bigger, more established presence and you have no way of meeting them in person, you can @reply them with witty rejoinders to their Twitter commentary, you can star their tweets, you can RT them, and you can add them to your Follow Friday list. The really pro way to do it is one #FF or #FollowFriday at a time.
#FollowFriday @brainpicker because Maria curates the most amazing pieces of my day from Rumi to Twain to John Cleese to Asimov.