Wal-Mart Stores Inc. (NYSE: WMT) is warning its workers over possible associate walkouts during this week’s big Thanksgiving shopping rush. Unions and labor activists have been promoting the possible walkout later this week. Wal-Mart also has a regional headquarters in Phoenix. Wal-Mart is Arizona largest private employer and the nation’s largest retailer. The company has also long been targeted by labor unions and activists who don’t like some of its business practices and its non-union…