When can workers be fired for Facebook posts and tweets?

Amy McClenathan apparently was having a bad day when she posted on Facebook, around the one-year anniversary of her mom's death, that some days she wished she would be fired so she could just stay at home. The next day she got her wish; the title company for which she worked fired her, KTVK reports. McClenathan is hardly alone and, especially concerning government and union workers, who may have...