Tweet From Above and Tweet From Below (TFA/TFB) let you post anonymous messages on Twitter without creating an account or posting those messages in your own Twitter feed. And why would you want to do that?
Well, we thought of a gazillion reasons, but the most basic is this: You’re a Twitter user, and sometimes you want to respond to something in the Twitterverse without your comments being broadcast to your followers or attached to your name. Standard @replies are okay, but maybe you want to let an obnoxious Twitterer know it without starting a feud. Or maybe you’re a (dis)satisfied customer of one of the umpteen businesses on Twitter and you want to give them feedback without starting a “relationship.” Or maybe you just need to get something off your chest.