Wal-Mart, the world's largest retailer, launched a national advertising campaign to counter long-term critics of the company's employment policies. "Wal-Mart is working for all Americans. Some of our critics are working only for themselves," company president Lee Scott said in an open letter that was published as a full page ad in more than 100 newspapers, including the New York Times, Wall Street Journal and USA Today. Scott said it was time for the public to hear the "unfiltered truth" about Wal-Mart, and time for the company to stand up on behalf of a workforce that includes 1.2 million Americans....