Celebrities: John Mayer, Miley Cyrus, Demi Lovato
Tweet Formula: Ego + disappearing act + anti-climatic return

John Mayer wasn't the first celeb to ditch and return to Twitter. Miley Cyrus quit the micro-blogging service in 2009 and Chris Brown did nearly a week ago. Demi Lovato cited more serious reasons-"I just get myself into trouble," she told The Daily Mail-but now The X Factor star is right back where she started, retweeting compliments every five minutes.