Increasing numbers of employers are asking their workers to tweet. The popular micro-blog Twitter allows companies to promote themselves in 140 characters or less. So why limit press releases to the PR department? But employers in government and the military are trying to figure out how to make sure they retain control of the messages that get out on Twitter or Facebook. Rachael King is a contributing technology writer for Businessweek. She joins The Takeaway to talk about the next step in social networking.