This week in social media, Twitter got pretty bruised by Wall Street, Facebook bought a fitness app and got rid of a couple of its less popular mobile offerings, and Whisper's CEO Michael Heyward duked it out with TechCrunch's Michael Arrington. Meanwhile, Tumblr added a huge swath of customization options to its mobile app and the Federal Trade Commission officially chided Snapchat. It's time for Social Media Saturday!
