This weekend saw PR executive Justine Sacco embroiled in one of the most unusual Twitter gaffe firestorms you will ever see.Rising out of obscurity - followed by around 200 people before Friday - she came to top trending lists the world over after posting an offensive racist “joke” just before boarding a long haul flight.Despite the clear irony of a supposed public relations expert posting something as publicly insensitive as she did, her incommunicado status was what caught the world's imagine, with everyone asking #HasJustineLandedYet.When she did land, the severity of writing: “Going to Africa. Hope I don't get AIDS. Just kidding. I’m white!” hit home, and she lost her job at online media company IAC.Yet though her story is unique among the Twitter gaffes of the year, she is far from alone in making a fool of herself on social media.(independent.co.uk)ANN.Az