I wrote about the darkest day in the history of the internet.
In other words, favs, as they came to be abbreviated, were one more instance of Twitter's community understanding the power of the service more completely than the people who were building it. They added hashtags to organize content around keywords; retweets to spread content virally; and through brute force converted a near-useless bookmarking feature into a powerful multi-purpose tool. I've favorited more than 60,000 tweets over the years, and in that time I've come to appreciate how versatile that little button is. I use it as a kind of read receipt to acknowledge replies; I use it whenever a tweet makes me laugh out loud; I use it when someone criticizes me by name in the hopes that seeing it's one of my "favorite" tweets will confuse and upset them. It often works!