Everyone knows that Rihanna loves Twitter. And when she's not taking photos with strippers or stripping down for a Twit-pic, she's feuding with Hollywood. She's battled it out with Piers Morgan over her newly cropped 'do, engaged in a war of words with Joan Rivers over Chris Brown, fought and made up with Ciara, and partook in an awkward online feud with Chris Brown's then-girlfriend. One thing is for certain: Never get on RiRi's bad side. She'll take you down with her tweets.