Here's a great post on why staffing companies should adopt social media policies and why employees should be very clear about those policies.
From the employer’s standpoint this ownership issue is a prime reason why employers should adopt social media policies clarifying who owns the social media accounts and ownership rights when the employment relationship is terminated. For example, it may make sense to allow employees using LinkedIn to keep their accounts but cleanse them of information that belongs to the employer because of the employer’s financial investment in the site and to ensure the employee is no longer associated as a spokesperson for his former employer. As a strategy to minimize, and perhaps avoid litigation altogether, an agreement between the employer and employee delineating the post employment rights of both the employee and employer to the account would seem the most efficient way to deal with this issue.
Full Article: http://computerfraud.us/articles/think-you-own-your-linkedin-twitter-and-facebook-account-think-again